When Wei-Yin Chen takes the mound Tuesday night in Seattle, he will become the fourth Orioles rookie since 1954 to make 30 or more starts in his first major league season, joining Bob Milacki (36 in 1989), Tom Phoebus (33 in 1967) and Brian Matusz (32 in 2010). Chen is 6-4 with a 4.17 ERA and seven quality starts on the road this season. In his only start against the Mariners on July 3 at Safeco Field, Chen allowed two runs and two hits, with no walks and nine strikeouts, in 7 1/3 innings to outduel Felix Hernandez. He left with a 4-1 lead, but the Mariners rallied to tie before the Orioles scored in the ninth for a 5-4 victory. Chris Tillman will go for his eighth win tonight in his 12th start of the season. He registered seven wins in 36 career starts from 2009-11. Matt Wieters' two-run shot on Sunday gave him 21 homers this season, allowing the Orioles to join the White Sox as the only teams in baseball to have five players with 20 or more. The 2011 Orioles had four players with 20 or more. The Orioles haven't had five players with 20 or more homers since 2008. The Orioles lead the season series with the Mariners, 5-1, including a 2-1 record in Seattle. They've won five straight against the Mariners dating back to July 3. The Orioles are 38-31 in three Septembers under manager Buck Showalter. The 38 wins are third-most in the American League behind Texas (44) and Detroit (42).