Stats say: These prospects drove the ball best in '18

Here at MLB Pipeline, the ringing in of the New Year means we're that much closer to rolling out our 2019 preseason rankings. Until then, however, we're continuing to look back at some of the more impressive hitters from the '18 season.
The first installment of this new stats-based series examined 10 hitters who, based on specific batted-ball data from our Prospects Stats tool, seem poised for more success in 2019.
This week, we're breaking down a crop of last year's more successful hitters -- specifically, players who had the highest percentage of their line drives and fly balls go for hits. It's a roundabout way of highlighting which hitters drive the baseball the most effectively in absence of Statcast™ data.
There are some obvious caveats here, of course. Namely, that the numbers used represent raw data and therefore are not adjusted for league and/or park factors. Also, the sample looks only at hitters who rank among their club's Top 30 prospects and had at least 350 batted balls during the Minor League regular season.
Meanwhile, after identifying select players in the series' first installment, this week's list is presented in ranked order. The spray charts below display all line drives and fly balls by each player in the Minor Leagues during the 2018 season.
One notable name absent from the list is Vladimir Guerrero Jr. The game's top prospect doesn't appear here because he fell just shy of the minimum for BIP (350). Of the 328 balls Guerrero put into play last season, 26.8 percent (88) were line drives or fly balls that went for hits, which would rank him just outside the Top 10 on this list.
1. Colton Welker, 3B, Rockies' No. 2 (No. 94 overall)-- 31.2 percent 
Welker, 21, won the Class A Advanced California League batting title in 2018 with a .333 average. He also led the circuit in hits, tallying 151 in 114 games, and put together hitting streaks of 15 and 20 games along the way, all while showing the ability to lace line drives to all fields. His home/road splits (.572 SLG, 9 HR vs. .750 OPS, 4 HR) suggest that he did benefit from Lancaster's extremely hitter-friendly environment, and some evaluators are wary about his power potential as a result, but Welker's career .337 average in 232 Minor League games, as well as his feel for using the opposite field, provides reason for all-around optimism.

2. Austin Allen, C/1B, Padres' No. 25-- 30.0 percent
Spending all of 2018 in the Double-A Texas League, Allen totaled exactly 22 home runs and 31 doubles for a second straight year and finished second in the circuit in slugging (.506). The exit velocities he posted in the Arizona Fall League confirm that Allen hits the ball hard, and the 6-foot-2, left-handed hitter has long shown that he can get to his huge pull-side power during games. Meanwhile, Allen's overall production -- he was a .290/.351/.506 hitter in '18 -- stands to improve if he can make gains against same-side pitching.

3. Elehuris Montero, 3B, Cardinals' No. 7-- 29.8 percent
Montero made the jump to full-season ball for his age-19 season and garnered Class A Midwest League MVP honors after leading the circuit in batting (.322), slugging (.529) and OPS (.910). Altogether, he finished with a .315/.371/.504 line, 16 homers and 37 doubles in 127 games across two levels. The 6-foot-3, 195-pounder impresses evaluators with his knack for squaring up the baseball from line to line -- a product of his excellent hand-eye coordination, bat speed and barrel awareness -- though his power plays mostly to his pull-side at the present. That said, it's not difficult to envision many of Montero's doubles clearing fences as he adds strength to his projectable frame.

4. Kevin Kramer, 2B/SS, Pirates' No. 7-- 29.7 percent
A revamped swing with an emphasis on hitting the ball in the air paid immediate dividends for Kramer, as he finished with 35 doubles (second most in the Triple-A International League) and 15 home runs after going deep just 10 times over his first 233 pro contests. The power surge came with the tradeoff of an elevated strikeout rate, though it didn't keep Kramer from finishing second in the circuit's batting race (.311 average).

5. Alex Kirilloff, OF, Twins' No. 2 (No. 10 overall)-- 29.6 percent
Kirilloff showed no lingering effects from the Tommy John surgery that cost him all of 2017 as he produced an obscene .348/.392/.578 line with 71 extra-base hits (20 HR, 44 2B, 7 3B) over 130 games between the Midwest and Florida State Leagues, at age 20. The scouting supports the stats, too, as there might not be a more promising hitter in the Minors (save for Vladimir Guerrero Jr., of course) than Kirilloff. He shows a potential plus-plus hit tool from the left side of the plate, combining athleticism, bat speed and barrel control with a mature approach and a preternatural feel for using the entire field. Meanwhile, the fact that Kirilloff hit over half (11) of his home runs to the opposite field (in two largely pitcher-friendly tough leagues) portends at least plus power.

6. Peter Alonso, 1B, Mets' No. 2 (No. 58 overall)-- 27.9 percent
Alonso's power was well documented in 2018, and not just because he finished tied for the Minor League lead with 36 home runs. The right-handed slugger became a Statcast™ favorite when he launched a 113.6 mph moonshot homer during the Futures Game, and he furthered that reputation in the Arizona Fall League by hitting the ball harder (116.3 mph double) than any Mets player since Statcast™ started tracking data in '15. And if that wasn't enough confirmation of Alonso's prodigious power, he also parked a home run to center field (110 mph exit velo) on a 103 mph fastball from Nate Pearson in the annual Fall Stars Game.

7. Brent Rooker, 1B/OF, Twins' No. 7-- 27.7 percent
Rooker showed plenty of power in his first full season as he posted a 45.3 percent extra-base hit rate to finish among the Double-A Southern League leaders in homers (22, second) and doubles (32, first). An ability to consistently hit the ball in the air earned Rooker a spot in this series' first installment, and he has the potential to improve even more in that regard given his current swing-and-miss tendencies and pull-oriented approach.

8. Corey Ray, OF, Brewers' No. 2-- 27.5 percent
After a disastrous first full season in 2017, Ray bounced back to hit 27 home runs, 32 doubles and steal 37 bags over 135 contests to win the Double-A Southern League's MVP Award. Ray's emergence as a legit power hitter stemmed from him rediscovering his feel for driving the ball to all fields -- his seven opposite-field homers matched his entire homer total from '17 -- and he consistently hammered inner-half fastballs. The power-speed pairing should make Ray a useful big leaguer, but as a career .239 hitter who struck out at a 29.3 percent clip last season (and 31 percent in '17), it's fair to question the future value of his hit tool.

9. Nate Lowe, 1B, Rays' No. 13-- 27.0 percent
A 13th-round pick out of Mississippi State in 2016, Lowe followed a nondescript first full season with an absolutely massive breakout campaign in '18, hitting .330/.416/.568 with 27 homers, 32 doubles and 102 RBIs as he ascended from Class A Advanced Charlotte to Triple-A Durham. Behind improved bat speed and a looser, more athletic left-handed swing, Lowe showed that he could drive the ball over the fence to the biggest part of any park, while still exhibiting a discerning eye at the plate against increasingly advanced pitching.

10. Keston Hiura, 2B, Brewers' No. 1 (No. 30 overall)-- 26.9 percent
Hiura's MVP campaign in Arizona Fall League was a fitting end to an impressive first full season, in which he slashed .293/.357/.464 with 13 homers and 34 doubles while reaching Double-A. Simply put, the 22-year-old has a gorgeous right-handed swing, as he's short but explosive to the ball, with a knack for finding the barrel and impacting the ball with authority to all fields. As a result, Hiura, who projects as at least a plus hitter with plus game power, has the ingredients needed to become a middle-of-the-order force for Milwaukee in the near future.

The next 10 on the list
Josh Fuentes, 3B/1B, Rockies' No. 17 -- 26.8%
Eloy Jiménez, OF, White Sox No. 1 (No. 3 overall) -- 26.4%
Laz Rivera, SS, White Sox No. 28 -- 26.4%
Kevin Smith, SS/3B, Blue Jays' No. 6 -- 26.4%
Tyler Ramirez, OF, Athletics' No. 17 -- 26.2%
Christin Stewart, OF, Tigers' No. 6 -- 26.0%
Matt Thaiss, 1B, Angels' No. 5 -- 25.1%
Gavin Lux, SS/2B, Dodgers' No. 4 (No. 82 overall) -- 24.9%
Lane Thomas, OF, Cardinals' No. 21 -- 24.9%
C.J. Chatham, SS, Red Sox's No. 8 -- 24.9%