Lefty Jo-Jo Reyes faces the Blue Jays for the first time game series at Camden Yards.
Reyes, 26, was traded from Atlanta to Toronto in July 2010 and spent the remainder of the season in the minors. He began 2011 in the majors and made 20 starts with the Blue Jays, going 5-8 with a 5.40 earned run average before he was waived on Aug. 2.
Baltimore immediately picked him up and utilized him in a relief role a day later, then inserted him into the starting rotation where he's gone 2-2 in four outings, including a 6-1 win at Minnesota in his last start Thursday.
In that game, the second-round pick from 2003 allowed a run on five hits in six innings.
He's made one career appearance against Toronto while with Atlanta, dropping a decision after seven innings of one-run ball on six hits with five strikeouts.
On Tuesday, rookie Ryan Adams capped a two-run bottom of the 10th with an RBI single into the right-center field gap, sending the Orioles to a 6-5 win in the series opener.
With the Orioles trailing 5-4, Matt Wieters and Mark Reynolds worked consecutive leadoff walks against Brian Tallet (0-1). Pinch-hitter Jake Fox then knocked in the tying run with a one-out single to right before Adams connected. The ball bounced over the fence to end the game.
Willie Eyre (1-0) picked up the win despite giving up a go-ahead run in the top of the 10th.
Wieters cracked a two-run homer and Vladimir Guerrero added an RBI double for the Orioles, winners in seven of their last nine.
Brett Lawrie clubbed a three-run homer and Eric Thames added two doubles for the Blue Jays, losers in five of their last six.
Toronto starts rookie righty Henderson Alvarez, who takes the mound for the fifth time in his brief career.
The 21-year-old debuted on Aug. 10 with a start against Oakland and got a no- decision after allowing three runs on eight hits in 5 2/3 innings.
Another no-decision followed at Seattle five days later and Alvarez has dropped two straight since, losing at Oakland and home to Tampa Bay while the Blue Jays have been outscored, 11-2.
In 22 2/3 innings, he's given up 25 hits and 13 runs with five walks and 16 strikeouts.
Toronto has won eight of 13 meetings with the Orioles this season.