Attended Buhach Colony High School in Atwater, CA. Was selected by the Miami Marlins in the 39th round of the 2013 draft but did not sign and elected to attend Cal. Is the nephew of former MLB pitcher Blas Minor. Minor pitched six seasons in the Majors with Pittsburgh (1992-94), New York-NL (1995-96), Seattle (1996) and Houston (1997). Older brother, Jake Jefferies, was selected by Tampa Bay in the third round of the 2008 First-Year Draft. Jake played six MiLB seasons in the for Tampa Bay (2008-11) and Miami (2012-13), reaching Triple-A with New Orleans (Miami) in 2012 and 2013. Named All Pac-12 First Team in 2015 after going 6-5 with a 2.92 ERA. In three seasons at Cal he went 15-13 with a 2.77 ERA, 186 strikeouts and a 1.10 WHIP. Pitched for USA Baseball’s Collegiate National Team in 2015. Selected by Oakland in the first round of the 2016 First-Year Player Draft (37th overall).
2023
Missed the entire season recovering from Tommy John surgery on Sept. 9, 2022, his second time undergoing the surgery (also April 26, 2017).
2022
Picked up the win in his first start of the season but then lost each of his next seven starts before going on the injured list in mid-May…missed the remainder of the season after undergoing thoracic outlet surgery in June and “Tommy John” surgery in September...Was 1-7 with a 5.72 ERA and .767 opponents OPS in his eight starts...Allowed a .286 opponents batting average but walked just eight batters in 39.1 innings, an average of 1.83 walks per nine innings...His opponents batting average broke down to .243 (18-for-74) with a .624 OPS against lefthanded hitters compared to .322 (28-for-87) with an .888 OPS against right-handers…yielded three of his four home runs to righties....Allowed a .342 batting average with runners in scoring position…three of the four home runs he surrendered came with the bases empty...Went 0-4 in four starts in Oakland and is winless in six career appearances in the Coliseum....Was 0-4 with a 6.98 ERA and .881 opponents OPS in four starts at night, 1-3 with a 4.50 ERA and .644 OPS in four starts during the day…his career splits are 0-5 with an 8.06 ERA and .927 OPS in seven night games, 2-3 with a 3.82 ERA and .627 OPS in seven day games...Received one run of support or fewer in six of his eight starts and had eight runs of support total (1.83 RSA)....Was on his first Opening Day roster and earned the win in his first start in the third game of the season, a 4-1 victory at Philadelphia on April 10…shut out the Phillies in five innings of work and tossed just 48 pitches…then lost each of his final seven starts and compiled a 6.55 ERA and .814 OPS during the losing streak, which is a career-high and was the longest by an Athletic in 2022…the streak of seven consecutive starts with a loss is tied for the third longest such streak in Oakland history…the longest are a pair of nine-game streaks by Brian Kingman (Aug. 12-Sept. 25, 1980) and Mike Morgan (June 11, 1978-July 24, 1979)… received no runs of support in back-to-back starts on April 15 at Toronto and April 20 against Baltimore and lost both starts despite allowing three runs, two earned, in 10.1 innings… struck out a career-high five batters in a career-high 6.0 innings in his outing against the Orioles…that gave him a 1-2 record despite a 1.17 ERA over his first three starts…finished April 1-3 with a 3.26 ERA in four starts but then went 0-4 with an 8.10 ERA in four starts in May… tied for the most losses in the majors in May…allowed a career-high six runs on a career-high 11 hits in 5.0 innings in a 6-1 loss to Tampa Bay on May 2…the hits were the most by an A’s pitcher since Frankie Montas allowed 11 on June 14, 2018 against Houston…tossed a career-high 90 pitches…did not walk a batter and had three consecutive starts from May 2-13 without issuing a walk (16.0 ip)…tossed a career-high tying 6.0 innings in a 2-0 loss to Los Angeles (AL) on May 13…allowed a career-high tying six runs and walked a career-high tying three batters while striking out a career-high tying five in 4.0 innings in his final start, a 14-4 loss to Minnesota on May 18…was placed on the 10-day injured list May 20 retroactive to May 19 with nerve irritation in his right arm…underwent thoracic outlet surgery on his right arm June 13 in Dallas, Tex.…the surgery was performed by Dr. Greg Pearl…experienced discomfort in his elbow during his rehabilitation and had right elbow ulnar collateral ligament reconstruction and ulnar nerve transposition surgery on Sept. 9…the procedure was performed by Dr. Neal ElAttrache at the Cedars-Sinai Kerlan-Jobe Institute…it was his second “Tommy John” surgery as he previously had the procedure on April 26, 2017.
2021
Spent most of the season at Triple-A Las Vegas where he was 5-1 with a 4.91 ERA in 15 starts… also had two stints with Oakland and went 1-0 with a 3.60 ERA in five games, including one start, before his season ended on Sept. 18 when he was placed on the 10-day injured list with right elbow ulnar neuritis...Allowed a .208 opponents batting average with the A’s, which broke down to .185 (5-for-27) with a .661 OPS against right-handed hitters compared to .231 (6-for-26) with a .605 OPS against left-handers...Had a .296 opponents average with the bases empty, .115 with runners on base…opponents were 1-for-12 (.083) with runners in scoring position...Stranded all five of his inherited runners and first batters faced were 1-for-4 (.250) with a double...Tossed 5.0 innings in his start and more than 2.0 innings in three of his four relief appearances...His five wins with the Aviators were a minor league career high and he matched his best with 15 starts…also had career highs in ERA (4.91), opponents batting average (.288), hits (90), runs (44), earned runs (42), home runs (13) and walks (11)...Had a .316 opponents on-base percentage as he walked just 11 batters in 77.0 innings (1.29 per nine innings)…has walked just 23 batters in 176.1 career innings in the minors (1.17 per nine innings)...Struck out 68 for a strikeout-to-walk ratio of 6.18…has 189 career strikeouts for a strikeout to-walk ratio of 8.22...Based on a minimum of 75 innings pitched, he led Triple-A West pitchers in strikeout-to walk ratio, ranked second in fewest walks per nine innings, third in fewest pitches per inning (14.9), eighth in opponents on-base percentage and ninth in ERA...His opponents batting average broke down to .280 (44-for-157) with a .789 OPS against righthanded hitters compared to .297 (46-for-155) with a .830 OPS against left-handers....Allowed 23 of his 44 runs in the first two innings of a game for a 6.60 ERA…had a 3.83 ERA after that, including 1.93 in the third inning...Was 1-0 with a 3.58 ERA in five starts on four days rest, 4-1 with a 6.15 ERA in nine starts on five days rest or more...The Aviators were 4-5 in his no decisions and had a 9-6 (.600) record in his starting assignments…tossed six or more innings in seven of his 15 starts, allowed two runs or fewer eight times and walked one batter or fewer 12 times…had eight starts without a walk...Was rated as the A’s seventh-best prospect by Baseball America following the season...: Began the season on the Las Vegas injured list with right biceps tendinitis…was reinstated May 21 and tossed 4.0 scoreless innings in his Triple-A debut on May 24 against Salt Lake (7 h, 1 so)…had a no decision in an 8-5 loss…logged 4.1 scoreless innings and allowed just one hit in his second start on May 29 against Sacramento…was 1-0 with a 1.37 ERA and .225 opponents batting average over his first four starts through June 8…then allowed a career-high seven runs and issued a career-high three walks on June 14 against Reno but had a no decision in a 21-16 Aviators loss…surrendered three home runs in a game for the first time in his career…that began a four-start stretch where he went 1-1 with a 12.33 ERA and .408 opponents batting average…tossed a season-low 2.0 innings June 26 at Salt Lake… went 2-0 in five starts in June but had a 7.25 ERA, .323 opponents batting average and .969 OPS…struck out a career-high nine batters in 4.1 innings on July 3 against Sacramento but was charged with his only loss of the season…then went 1-0 with a 3.75 ERA over his next four starts before his first promotion to Oakland…allowed just one run in a career-high 7.0 innings on July 15 to defeat El Paso 5-1…matched his career high with nine strikeouts on July 20 against El Paso…allowed four runs on 10 hits in 5.0 innings July 26 against Salt Lake and was promoted to Oakland on Aug. 1…picked up his first Major League win that day in a start in the A’s 8-3 win at Los Angeles-AL (5.0 ip, 3 h, 3 r, 3 er, 3 bb, 3 so) but that would be his only outing before he was optioned back to Las Vegas Aug. 8…went 2-0 with a 4.00 ERA over his final three starts with the Aviators…logged 6.0 scoreless innings on Aug. 15 against Tacoma and tossed a career-high 96 pitches…yielded a career-high tying seven runs on a career-high 12 hits in 6.0 innings in his final start with Las Vegas on Aug. 20 against Albuquerque but had a no decision in a 12-7 win…was recalled by Oakland on Aug. 27 and compiled a 2.70 ERA and .222 opponents batting average in four relief appearances, all in A’s losses…pitched in relief for the first time in the majors on Sept. 1 at Detroit (1.0 ip, 2 h, 1 r, 2 so)…it would be his shortest outing as a reliever as he logged 2.1 scoreless innings Sept. 4 at Toronto, 3.1 innings Sept. 7 vs. Chicago (AL) and 3.1 scoreless innings Sept. 12 vs. Texas…was placed on the 10-day injured list Sept. 18 retroactive to Sept. 15 with right elbow ulnar neuritis and missed the remainder of the season.
2020
Made his Major League debut after being added as the 29th man for the Sept. 12 doubleheader at Texas…started the first game and was the losing pitcher in the A’s 5-2 loss…allowed five runs on five hits and two walks in 2.0 innings…fanned Nick Solak in the first inning for his first ML strikeout…allowed five runs in the first inning on a three-run home run by Odor and a two-run home run by Guzman…then retired three of four batters in the second…was on the A’s Taxi Squad for each of the final two road trips of the regular season and the postseason…made one Spring Training appearance (0.2 ip, 3 h, 3 r, 3 er, 1 bb) before he was optioned to Triple-A Las Vegas March 6…was added to the A’s 60-man player pool June 29…was rated as the A’s number three prospect by Baseball America following the season.
2019
Combined for a 2-2 record and a 3.42 ERA in 26 games, including 15 starts, with Single-A Stockton and Double-A Midland in his first full season following 2017 "Tommy John" surgery…struck out 93 batters in 79.0 innings, an average of 10.59 per nine innings…walked just 11 (1.25 per nine innings) for a strikeout-to-walk ratio of 10.3…was named the A's Organizational Pitcher of the Year…saw limited duty when he pitched, as he tossed exactly 3.0 innings in 24 of his 26 appearances…logged 3.1 innings and 3.2 innings in his other two outings…averaged 45.2 pitches per game…began the year with the Ports and was 1-0 with a 2.40 ERA in five games, three starts, when he was promoted to the RockHounds April 29…went 1-2 with a 3.66 ERA in 21 games, 12 starts, in his Double-A debut…combined with both clubs for a .242 opponents batting average, including .213 (31-for-145) against left-handed hitters compared to .268 (42-for-157) against right-handers…surrendered five of his eight home runs and issued seven of his nine walks to lefties…issued just one walk to batters leading off an inning…compiled a 2.48 ERA in 19 games at night compared to a 6.00 ERA in seven day games…was 0-1 with a 2.36 ERA in his 15 starting assignments compared to 2-1 with a 4.86 ERA in 11 relief appearances…walked one batter or fewer in 25 of his 26 appearances…was rated as the A's number four prospect by Baseball America following the season.
MINORS: Was credited with the first win of his professional career on Opening Day when he tossed 3.0 scoreless innings of relief on April 4 against Rancho Cucamonga…pitched 3.0 scoreless innings in each of his final two appearances with Stockton on April 19 against Modesto and April 25 at Visalia…was promoted to Midland on April 29 and did not walk a batter in his first eight games (24.2 ip)…allowed five runs over his first three outings through May 12 (9.0 ip, 5.00 ERA)… then was tagged with the first loss of his career in a start on May 17 at Corpus Christi when he allowed one unearned run in 3.0 innings in the RockHounds 1-0 loss…that began a five-game stretch from May 17 to June 7 where he allowed just three runs, two earned, in 15.2 innings (1.15 ERA)…tossed a season-high 3.2 innings June 7 against Frisco…also struck out a career-high six batters, his first of four six-strikeout games in 2019…allowed season-highs in runs (5) and hits (6) June 13 at Springfield but then allowed one earned run in each of his next five appearances (3.00 ERA)…logged a season-high 66 pitches in 3.0 innings June 18 against Springfield…matched his season-highs by yielding five runs on six hits July 14 against Corpus Christi…then tossed 3.0 scoreless innings in back-to-back outings on July 19 at Tulsa and July 25 against Arkansas to begin a season-ending stretch where he posted a 2.50 ERA over his final six appearances…walked two batters July 25 against Arkansas, his first career outing with more than one walk…allowed two runs in 3.0 innings of relief Aug. 15 at Amarillo for his second win…went on the injured list the next day with a right pectoral muscle strain and missed the remainder of the season.
