The Orioles right-hander, scheduled to be called up and added to the active roster and make his first start of the season on Wednesday, is 7-15 with a 5.58 ERA in parts of three Major League seasons.
But after going 5-1 with a 1.96 ERA in his last three starts with Triple-A Norfolk, Tillman is hoping to find a home in a rotation that has two spots up for grabs.
"I'm happy with where I'm at and I'm confident in it," Tillman said. "I think that's the most important thing, being confident in it."
Also looking for a fresh start is Mariners right-hander Hector Noesi, who is 2-10 with a 5.69 ERA this season.
Noesi has shown flashes of success, throwing four scoreless innings against the Red Sox on Friday before allowing five runs on four homers in the next 1 2/3 innings.
"Good early, was rolling along, then he creeped up in the zone," Mariners manager Eric Wedge said. "You saw what happened then, creeped up in the zone, the ball flattened out on him and they started turning the baseball around. Happened quick, happened quick."
Noesi has consistently struggled to keep the ball down, yielding 19 home runs in 16 starts.
Noesi's 10 losses tie him with Baltimore left-hander Brian Matusz for most in the American League, although Matusz was demoted to Norfolk following his most recent outing.
Tillman will be hoping to pitch well enough to stay in Baltimore.
Orioles: Roberts heads to DL
• The Orioles placed second baseman Brian Roberts on the 15-day disabled list with a right groin strain on Tuesday.
Roberts has hit .182 in 17 games after sitting out the season's first two months with concussion symptoms.
• Robert Andino started at second and hit the game-winning home run in the ninth, while Xavier Avery took Roberts' place on the 25-man roster, started in left field and went 3-for-5 batting leadoff.
• Rule 5 Draft Pick Ryan Flaherty started at third base and went 1-for-3 on Saturday, his fifth consecutive start with a hit.
Mariners: Saunders, Smoak notch hits in return
• After missing the past four games with an intestinal flu, Michael Saunders returned to the lineup on Tuesday and hit a double in the eighth.
Justin Smoak also returned to the lineup after sitting out on Monday and hit an RBI single in the eighth to break a 2-for-32 slide.
• Jesus Montero is hitless in his last 21 at-bats.
• Baltimore's win on Tuesday was the 200th against Seattle in franchise history.