Washburn was upstaged by Brian Matusz, who looked stellar in his major league debut, as Baltimore routed Detroit 8-2 on Tuesday night.
"I was terrible," Washburn said.
He also admitted that he was a little more nervous than usual because he wanted to get off to a good start with his new team.
Washburn was a couple of days off of his usual schedule. This past Sunday would have been his normal day to pitch, based on the Seattle rotation.
But he refused to lean on that.
"No excuses. I didn't do my job," he said. "I didn't have command."
Tigers' manager Jim Leyland isn't worried about Washburn.
"He was rusty. You could see his command wasn't there," Leyland said. "... He's not going to be an issue for us. He's going to be good for us. We have other things much worse than that."
Matusz (1-0), the fourth pick overall in the 2008 draft, allowed a run and six hits in five innings in his major league debut. He walked three and struck out five.
"He has tremendous mound presence and has command of four pitches. He is going to be a top of the rotation starter," Orioles' manager Dave Trembley said. "He's going to be good for a very long time ...This night belonged to him."
Matusz was 7-0 with a 1.55 ERA for Double-A Bowie before being recalled on Tuesday.
"It [major league debut] came really fast. It was something that I dreamed as a kid," he said. "I was ready ... I won't fool you, I was nervous. After the first strike I calmed down a bit but it was tough working on my mechanics all night."
Washburn (8-7), who was acquired from Seattle on July 31 in a deal for pitchers Luke French and Mauricio Robles, gave up six runs and six hits in 5 1/3 innings. The six runs allowed matched a season high for him.
Like Detroit's continued lack of offense and inability to get hits with runners in scoring position.
Matusz worked out of a bases-loaded, two-out jam in the second, thanks to Izturis' diving stop at short on Adam Everett's grounder up the middle. Izturis then flipped to second baseman Brian Roberts for the force out.
"We let him off the ropes," said Tigers' catcher Gerald Laird. "But you have to give him credit."
The Orioles blew open a tight game in the sixth with four runs to make it 7-1.
Markakis hit a two-run homer that was estimated at 442 feet and Izturis added a two-out, bases-loaded two-run single.
"We did the job up and down the lineup tonight," Markakis said. "We got the big hits when we needed them and the pitching was just super."
Melvin Mora added a RBI single in the seventh.
Baltimore scored in each of the first two innings to take a 2-0 lead.
Markakis' RBI single opened the scoring in the first, one out after Roberts greeted Washburn with a leadoff double off the left-centerfield fence.
Matt Wieters' single made it 2-0 in the second.
Detroit scored on Everett's double in the fourth and Magglio Ordonez's single in the ninth.
Izturis restored the Orioles two-run lead with a two-out homer in the fifth. It was his second of the season and first since opening day.
Detroit recalled OF Wilkin Ramirez from Triple-A Toledo and optioned RHP Casey Fien to the same team. Ramirez started in left field and batted leadoff in the game. ... Baltimore optioned RHP Kam Mickolio to Triple-A Norfolk to make room for Matusz. ... After the game, the Tigers optioned Ramirez and C Dusty Ryan to Triple-A Toledo and recalled the option of RHP Chris Lambert from Toledo and recalled C Albert Avila from Double-A Erie. ... Matusz is the fifth Orioles' pitcher to win his major league debut this season. That's the second most for one team in one season in major league history