BALTIMORE -- With one flare to left field, Mark Trumbo helped the Baltimore Orioles end a frustrating day on a high note.

Trumbo had a game-winning RBI single in the bottom of the 12th inning and Baltimore split a four-game series with a 5-4 victory against the Toronto Blue Jays on Sunday. Prior to Trumbo's hit, the Orioles had gone 0 for 16 with runners in scoring position.

"I don't think anyone really noticed it," said Trumbo, who also homered. "It didn't feel like we were coming through all that often, but we don't dissect it like that. You just do what you can. When you get the opportunity, then you want to come through."

Welington Castillo hit a pair of homers, including a game-tying solo shot in the ninth as Toronto closer Roberto Osuna squandered an opportunity to tie a career-high with his 36th save.

"I started with three fastballs away, so I didn't think he was going to hit that cutter," Osuna said. "It was my decision. It was my fault. I left it a little bit up. He had a good swing on it."

Jonathan Schoop led off the 12th with a double off Danny Barnes (2-6), and two batters later, Trumbo stroked the ball into the left-field corner for the winner.

The Orioles kept pace in the American League wild-card standings and open a crucial three-game series with the New York Yankees on Monday.

"You can't sit here and talk about all the contributions and things that had to happen to get to that opportunity," Orioles manager Buck Showalter said. "You had some situations where you look like you're going to push it across and you let that snowball. You can't let things snowball, especially this time of year where something negative happens, and when something positive happens get comfortable with it. The players are just too good."

Baltimore tied the game 3-3 in the sixth when Schoop led off with a double, took third on a fielder's choice and scored on a sacrifice fly by Trey Mancini.

Ryan Goins responded for Toronto when he doubled off the glove of Orioles third baseman Manny Machado in the seventh and scored on a pinch-hit single by Michael Saunders off Darren O'Day.

Josh Donaldson had a three-run home run for the Blue Jays and now has 25 on the year.

The Blue Jays played without manager John Gibbons, who missed his second straight game because of a personal issue. Bench coach DeMarlo Hale ran the club in Gibbons' absence.

Toronto leads the majors with 13 walk-off losses.

"I didn't know it was that many," Hale said. "It also shows that we're in games. We're competing for those nine-inning or however many innings it takes. Osuna has been good. He just didn't execute that one pitch."

Orioles starter Chris Tillman got into trouble in the third when he allowed a one-out walk to Richard Urena and a single to Teoscar Hernandez. Donaldson then hit an 0-1 fastball over the center-field wall for a 3-0 lead.

Castillo got the Orioles on the board in the bottom half when he led off with a homer to left off left-hander Brett Anderson. Making his second start for Toronto, Anderson was effective through six innings, allowing three runs and three hits with three strikeouts.

Trumbo pulled Baltimore within 3-2 with a solo homer in the fourth. A walk to Urena in the fifth ended the day for Tillman, who allowed three runs and three hits with two strikeouts and three walks over four-plus innings.

Tillman is now winless in his past 18 starts. His last victory came on May 7 in his season debut. He had earned at least 10 wins in each of the past four seasons.

"Right now is the time of year we've got to win, especially in September," Tillman said.

NOTES: Orioles SS J.J. Hardy received a cortisone injection in his elbow Friday. He threw Sunday and will hit the following day if there are no setbacks. ... Toronto RHP Chris Rowley was recalled from Triple-A Buffalo. He has appeared in two games for the Blue Jays this season, going 1-1 with a 4.61 ERA. ... Baltimore recalled RHP Gabriel Ynoa was recalled from Triple-A Norfolk. RHP Alec Asher was optioned to Double-A Bowie to continue pitching on a regular schedule.