"The cycle of a player's time in an organization comes and goes, and maybe my time is nearing its end," he said.

Robertson came to the Tigers in 2003, has gone 49-65, and pitched well in the 2006 postseason. But he was 7-11 with a 6.35 ERA last year, had an up-and-down spring, and did not make the rotation that includes Justin Verlander, Edwin Jackson, Zach Miner, rookie Rick Porcello and Armando Galarraga.

Jeremy Bonderman (shoulder) could return in the next month to start, further impacting Robertson's chances of a quick return to the rotation.

"If someone had told me in 2006 that Robertson would be in the bullpen, I'd have told him, 'You are crazy,' " Tigers manager Jim Leyland said. "But it's an opportunity for Nate to help a very good ballclub and show he can get back to the point of starting."

Robertson said his command last year was not the problem, but rather what happened when the ball was in the strike zone. That, in essence, is why Robertson is not starting.

Leyland evaluates his pitchers by their results when they pitch strikes. Robertson often was hit hard in 2008, leading the American League with 119 earned runs allowed and tying for fifth in the league with 26 home runs allowed.

Robertson said his slider is back with good velocity and bite. But he is adjusting his pitching approach because of a drop in fastball velocity.

"There is no doubt in my mind I can start in the big leagues," said Robertson, who was 2-1 with a 5.52 ERA in Grapefruit League games. "I believe there is a plan for me here or somewhere else as long as I am healthy, God willing."

Robertson praised his manager, teammates and front office, adding he loves living in suburban Detroit.

"But there is a wind of change," he said. "No hard feelings. It's the business of the game.

"I want to be someplace where they have confidence in me. But I understand that confidence was shaken last year."

He added pitching out of the bullpen "is a difficult mind-set" and he never has pitched well in relief. Robertson has a 4.83 ERA in career starts and an 8.83 ERA as a reliever.

"Do I hope he returns to his starting position?" Leyland said. "Absolutely."

"But that's up to Nate Robertson."

Robertson is due $7 million this year and $10 million next season ($11 million if he pitches 200 innings in '09). That will make trading him difficult unless the Tigers are willing to eat a significant amount of his contract.

Leyland said he thought all roster decisions he made along with general manager Dave Dombrowski and his coaches were fair.

"Nobody on this team has a complaint," Leyland said. "But there are two people not on this team who have a complaint."

He was referring to left-handed reliever Clay Rapada, who had a strong spring, and outfielder Ryan Raburn, a valuable bench player last year who simply wasn't as good a fit on this year's team.

Rapada likely would be on the team had Porcello been sent to the minors for seasoning with Robertson going to the rotation.