(AP) — J.A. Happ is certainly exceeding expectations for the Seattle Mariners.

Happ goes for his longest single-season winning streak in six years Thursday night when the Mariners try to conclude this three-game set with back-to-back wins over the Baltimore Orioles.

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Happ (3-1, 2.98 ERA) was acquired from Toronto in exchange for outfielder Michael Saunders in December after spending his first eight seasons with Philadelphia, Houston and the Blue Jays.

The left-hander, though, only had one winning season, going 12-4 with a 2.93 ERA with the Phillies in 2009 and was runner-up in NL Rookie of the Year voting.

Happ has been impressive with Seattle (18-21), compiling the second-best qualifying ERA on the staff behind Felix Hernandez’s 2.30, and his 1.79 walks per nine innings is among the best in the AL.

He’s 3-0 over his last five starts while allowing two or fewer runs in four of them, and he hasn’t put together a longer winning streak since reeling off six in a row from May 15-July 19, 2009.

Happ used his changeup to limit Boston to one run in seven innings before Nelson Cruz’s walkoff single in Friday’s 2-1 win.

“He has his confidence back in that pitch,” pitching coach Rick Waits told MLB’s official website. “It wasn’t working early in the game, but he got it going. He understands he has to have that fourth pitch in his arsenal, and he has enough confidence in it that he kept throwing it.”

Happ is 2-3 with a 2.93 ERA in eight games – seven starts – against the Orioles, giving up five runs and two homers in a 6-1 loss at Baltimore (17-20) on Sept. 17.

The Mariners beat the Orioles 4-2 on Wednesday for just their second win in nine road games.

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Cruz has been productive in his return to Baltimore, going 4 for 7 with one homer, one double and three RBIs in two games. He’s hitting .409 over the past 12 games, lifting his season average 24 points to .351 to rank among baseball’s leaders.

Justin Ruggiano also has four hits in this series after connecting for a two-run homer and a double Wednesday. He’s 8 for 16 in four games at Camden Yards.

The Orioles are turning to Chris Tillman (2-5, 6.34), who has a 2.03 ERA while winning all six of his starts against the Mariners – four at home.

The right-hander, though, has lost a career-high four straight starts with a 6.85 ERA, and he’ll try to overcome stiffness in his lower back that’s sidelined him since a 10-2 loss to Toronto on May 12. He gave up five runs and nine hits in 6 2-3 innings.

“I’m not all that concerned about it,” Tillman told MLB’s official website. “I’ve had it before. It kind of happened in my bullpen. Trying to be careful with it and not make it worse than it has to be.”

Tillman has lost both of his home starts, surrendering 12 runs and 16 hits – three homers – in 9 1-3 innings.

He’s held Cruz to 1 for 8 with a homer, but Robinson Cano is 12 for 28 (.429) with two home runs off him.

Baltimore’s Adam Jones has a .377 average at home after going 6 for 13 in the last three games there. However, he went 2 for 14 with a homer versus Happ last year.

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(Copyright 2015 by The Associated Press. All Rights Reserved.)