His last two outings against the Tampa Bay Rays suggest he's still the team's biggest strength in an ever-changing rotation.Chen looks to rebound from arguably his worst outing of the season and help the Orioles maintain at least a share of first place in the AL East on Thursday against the Tampa Bay Rays.Baltimore's remarkable season continued with yet another one-run victory Wednesday, 3-2 over the Rays as Nate McLouth's single off the right-field wall in the bottom of the ninth scored Manny Machado.With their 13th win in 18 tries, the Orioles (80-62) remained tied with the Yankees atop the East and moved three games clear of the third-place Rays (77-65). Baltimore moved 18 games over .500 for the first time since the end of 1997, the year of its last winning season and most recent playoff appearance."It's neat because almost daily you can kind of sense and feel the excitement growing a little bit," McLouth told the team's official website.Although the Orioles' 13-game streak of one-run wins was snapped Sept. 1 in New York, they are 26-7 in games decided by the slimmest of margins. The Rays, meanwhile, have lost 12 of their last 15 one-run contests."In the past we've been a great team in close ball games," center fielder B.J. Upton said. "This year it hasn't been that way."Tampa Bay is 2 for 14 with runners in scoring position in the first two games of this series and will try to avoid being swept at Camden Yards for the first time since May 8-10, 2007.To do that, they'll have to find a way to generate more offense. Since allowing 10 runs to the Rays on July 25, the Orioles have held them to eight over the last six games. Tampa Bay has lost five of six and is 3 for 38 (.079) with runners in scoring position during that span."That's typical of why we're several games behind right now," manager Joe Maddon said. "We have had great pitching, but we're not getting a hit when we need it."Chen (12-9, 4.06 ERA) will try to send the Orioles off on a winning note before they open a nine-game road trip Friday against wild card-leading Oakland.The rookie lefty, one of 11 starters used by Baltimore this year, was tagged for a season high-tying seven runs and surrendered three homers over 4 2/3 innings of an 8-5 home loss to the Yankees on Friday.Chen has allowed five or more runs in half of his past six starts, posting a 6.55 ERA while yielding nine home runs in 33 innings during that stretch.He tossed seven innings in a 4-0 victory at Tropicana Field on Aug. 4, and is 1-1 with a 1.98 ERA in his last two starts against the Rays.Jeremy Hellickson (8-10, 3.33) is plenty familiar with the Orioles, having already made four starts against them this season. He is 1-2 with a 3.42 ERA in those outings, including 1-0 with a 2.77 ERA in two at Camden Yards.The right-hander is 0-2 with a 3.71 ERA in his last three starts overall, allowing only three runs and eight hits in his past two appearances, spanning 12 innings.Hellickson was very good against Texas on Friday but left without a decision after giving up a solo homer to Michael Young and three other hits over six innings of an extra-inning win.He'll want to pitch carefully to Adam Jones, who is 8 for 25 (.320) with three homers lifetime versus Hellickson.