Chen, the team leader in ERA, has dominated back-to-back starts and now looks to match a career high with his third consecutive victory Wednesday night when the visiting Orioles go for their fifth straight series win.
After getting denied a four-game sweep in Oakland with Sunday's 9-8, 10-inning loss, Baltimore (16-11) had its eight-game winning streak over Seattle snapped with Monday's 6-2 defeat.
The Orioles, though, avoided a season high-tying third consecutive loss with Tuesday's 7-2 victory. The Mariners (12-17) had won their previous three games while allowing five runs.
Baltimore has won six of seven in Seattle, and Chen (2-2, 2.53 ERA) pitched well in two starts there last season but didn't win either one. The Mariners did win both, however, as he allowed four runs and struck out 11 in 12 2-3 innings.
Chen has posted four straight quality starts and was brilliant in winning the last two, surrendering five total hits and one run in 14 innings. He went a career-high eight innings in Friday's 3-0 victory over the A's.
"Not physically, but mentally, I think this is probably the best start I have had in the major leagues," Chen said through an interpreter.
Chen, who won a career-best three consecutive starts from June 6-17, hopes to provide another lengthy outing to help save the bullpen. Baltimore's relievers have had to pitch 12 2-3 innings in four games since Chen's last outing.
The Mariners' bullpen might see plenty of action as well if Wednesday's scheduled starter, Aaron Harang (0-3, 11.37), runs into more problems. Since he arrived from Colorado via trade last month, the veteran right-hander has lost each of his three starts while totaling 12 2-3 innings.
This could be a make-or-break start if Harang plans on keeping his spot in the rotation.
"I'm not concerned," manager Eric Wedge told the Mariners' official website after Harang permitted five runs in three innings of Friday's 6-3 loss to the Los Angeles Angels.
"... He's a veteran pitcher. He knows how to win at this level, and I'm sure he'll be better next outing."
Harang, whose opponents are batting .362, could get an early test with Nate McLouth, whose 11th career leadoff homer opened a four-run first inning Tuesday. McLouth is batting .485 with 14 runs in his last nine games and has seven RBIs over his past six.
McLouth, though, is 3 for 27 against Harang with 11 strikeouts, his most against any pitcher.
Orioles third baseman Manny Machado, who has yet to face the right-hander, will try to extend his team-best hitting streak to 10. He's batting .410 over the last nine.
Mariners second baseman Dustin Ackley has lifted his batting average from .145 to .253 during a 10-game hit streak. Ackley is 1 for 5 against Chen.
The southpaw, giving up a team-low .56 homers per nine innings, has not allowed a home run to any current Mariner.
Seattle's Michael Morse, who has two of his team-high eight homers in the last three games, is 2 for 3 against Chen - both singles.