BALTIMORE -- Before factoring in Wednesday’s late-inning meltdown against the Blue Jays at Camden Yards, the Orioles owned the American League’s best bullpen by ERA since August 20. The O's relief corps' mark of 3.70 ERA in September was better than the Yankees, the Astros or the Rays. Even for just that small span of time, it's a notable improvement, given how Baltimore’s ‘pen ranked as baseball’s worst for the season’s first four months.

Part of that success was the emergence of Hunter Harvey, the post-Deadline resurgence of Mychal Givens and a strong September from Shawn Armstrong. But a big part of the 'pen turnaround has been Miguel Castro, who has simply improved like few other relievers in MLB over the entirety of the season.

“His confidence is at an all-time high right now,” Orioles manager Brandon Hyde said of Castro. “I hope this is what he is -- a guy who can come in against tough right-handed hitters and be able to put them away.”

Castro had been exactly that for the better part of five months now, holding righties to a .152 opponents' batting average since May 1 before Wednesday's nightmare outing (five earned runs on three hits and two walks in two-thirds of an inning). Of course, one night does not make a season, nor constitute a trend.

For a better example of the pitcher Castro's been, look to Tuesday, when Castro powered through the heart of the Blue Jays’ lineup with ease, striking out Lourdes Gurriel Jr., Vladimir Guerrero Jr. and Randal Grichuk on 14 pitches. Each third strike came swinging on a slider, a pitch that Castro is throwing more in September than any at any point this season.

“The aggressiveness in the strike zone and getting his fingers on top of that slider has really been the difference,” Hyde said. “Earlier in the year, you saw a lot of arm-side misses underneath the ball, fingers on the side of the ball -- frisbee sliders. And now, the slider is really going down with some bite.”

The results have been plain to see. Castro was unscored upon in his first seven appearances this month, slicing his ERA from 8.59 in March/April to an above-league-average 4.14 entering play Wednesday. It's inflated to 4.73 now, but Wednesday was Castro's first major setback since mid-May.

Way more common has been consistent improvement, with Castro pitching to a 4.63 ERA in May, 3.07 in June/July and a 2.92 mark in August.

Since finishing May with an ERA north of 6, Castro had allowed a line of .185/.294/.293 with a 2.58 ERA before Wednesday. Just three of his 10 homers allowed have come in the second half.

“I think the key is being consistent with my mechanics,” Castro said, through team interpreter Ramón Alarcón. “I feel like I trust all of my pitches more, and I’m more confident in throwing all of them for strikes in any given count.”

Castro specifically credited an increased ability to finish his delivery more consistently (“When I’m about to keep my lower half in sync, it allows my upper half to go with it,” he said) leading to better command. That was always the issue with Castro, whose 6-foot-7 frame and raw talent (97th-percentile fastball velocity) always made scouts salivate, but who bounced from the Blue Jays to the Rockies to the Orioles in three trades before he turned 23.

Now in his age-24 season, Castro appears to have turned a corner. He’s improved his strikeout rate from 16 percent in 2018 to 22 percent this season, while cutting his walk rate from 13.3 percent to 12.7 percent. He’s bumped his sinker velocity from 95.4 mph to 97.3 mph, as MLB.com’s Mike Petriello noted in June.

Among 121 pitchers who faced at least 300 hitters in each of the past two seasons, Castro’s 69-point jump in the advanced Statcast metric xwOBA colors him as MLB’s second-most improved hurler in that stretch.

“Every day I want to be better than the last time I was out there,” Castro said. “Things have evolved to where they are now, but the whole idea is to improve every day.”

From the trainer’s room
A day after passing concussion protocol following a crash into the center-field wall, Mason Williams said he remained symptom-free on Wednesday afternoon. However, a return to the field remains up in the air for Williams, who couldn’t say whether or not he’ll play again this season.

“The wall won,” Williams said. “That one hurt a little bit.”

Williams said he mostly lost his breath on the play, though his left knee remained sore as well. He called it “not something I want to do again,” but relented he would rather approach similar balls with less aggressiveness. One of Baltimore’s September callups after a productive year at Triple-A Norfolk, Williams, 28, is 8-for-30 (.267) with two RBIs in 11 games since being recalled.

Pitching plans
The Orioles are skipping right-hander Aaron Brooks’ turn through the rotation, starting right-hander Gabriel Ynoa on Thursday in what would’ve been Brooks’ spot. Brooks won last time out in Detroit, but it’s been a struggle for the right-hander since coming over from the A’s on a waiver claim in July. Brooks is 3-5 with a 7.11 ERA in 12 starts for Baltimore, and 5-8 with a 6.06 ERA in 27 games (18 starts) this season overall.

Hyde said the club will go with a bullpen day on Friday against the Mariners, then deploy Asher Wojciechowski and John Means on Saturday and Sunday, respectively. Both pitchers will be on an extra day of rest, as has become standard operating procedure for the Orioles down the stretch.