SEATTLE -- Pitcher Chris Tillman was in the Orioles' clubhouse on Tuesday afternoon, as the 24-year-old will be activated and make his season debut in Wednesday's series finale against the Seattle Mariners.

"This is what I've worked all season for," said Tillman, who had an impressive spring and flew, along with outfielder Xavier Avery, to the West Coast early Tuesday morning from the team's Triple-A affiliate in Norfolk. "I've gotten in a good routine and it's working well. I'm real excited."

Tillman is 8-8 with a 3.63 ERA and 92 strikeouts in 89 1/3 innings in 15 starts with Norfolk this season and said Tuesday he still wasn't sure what was up even when he was scratched from Monday's start. He threw a bullpen session instead and was told by Tides manager Ron Johnson afterward that he was getting the call to join the Orioles.

While excited for the opportunity, Tillman stressed carrying over the same routine that has made him successful with Norfolk and hopes to avoid the pitfalls that have resulted in a shuttle back-and-forth from the Majors to the Minors over the past three seasons. He is a career 7-15 with a 5.58 ERA in 36 games.

"I was on a pretty good run down there," said Tillman, who has posted a 2.88 ERA in his last 10 starts, posting 66 strikeouts against 15 walks over that stretch. "Having guys like Jamie Moyer and J.C. Romero down there really helped. I can't tell you how cool that was, and talking to them about your routine. I think I learned a lot working down there.

"I'm happy with where I'm at and I'm confident in it. I think that's the most important thing, being confident in it."

Right-handed reliever Steve Johnson was optioned to Norfolk to make room for Tillman on the 25-man roster.

Worth noting

• Nick Markakis (right wrist) amped up his efforts in Tuesday's batting practice with short-season Aberdeen with positive reports, according to manager Buck Showalter. The team is hoping Markakis can start playing rehab games as early as Thursday.

• Endy Chavez started running at the team's spring complex in Sarasota, Fla. He is nursing a left hamstring strain.

• Taylor Teagarden served at designated hitter for the Gulf Coast League Orioles on Tuesday, going 1-for-3 with a walk.