DETROIT -- The fatigue factor took a back seat to the adrenaline rush right-hander R.A. Dickey felt on Thursday morning when he walked into the visiting clubhouse at Comerica Park.

A red-eye flight from Seattle to Detroit got him here in time to suit up for the Mariners' series afternoon finale against the Tigers, and he looked like someone who had not slept much.

"Yeah, I am tired," he said.

Tired, but ready to resume his Major League career.

The 33-year-old knuckleball specialist was added to the 25-man roster prior to the series finale, replacing right-hander Cha Seung Baek on the Mariners' 12-man pitching staff. Baek was designated for assignment following Wednesday night's 9-4 loss to the Tigers.

The Mariners have 10 days to trade, release, option or assign Baek outright to the Minors.

Dickey, who started seven games for Triple-A Tacoma and compiled a 2-5 record and 3.44 ERA, will begin his second stint with Seattle this season as a reliever.

"We have been talking about this for awhile," manager John McLaren said of the latest personnel move. "The thing about Dickey is he has versatility. He can throw long and pitch the next day, or the day after that, which helps us a little bit."

The Mariners bullpen was used extensively in the first two games of this series.

Right-hander Carlos Silva went four innings in Tuesday night's series opener and left-hander Jarrod Washburn lasted just 2 1/3 innings on Wednesday night.

Though he was used exclusively as a starter with Tacoma, there is no indication that he'll move into Seattle's rotation, which has struggled this month.

Dickey said any role is fine with him.

"I can pitch multiple innings on multiple days, and there has been a need for that lately here," he said. "I am finally, mentally, [ready] to do that. I have pitched out of the pen before."

One of his two appearances with the Mariners last month came in a starting role. He started and absorbed the loss in a game against the Angels in Anaheim on April 18.

Four days later, he was sent back to Tacoma.

"My knuckler is a little more consistent now than it was then," he said. "I went back down there to work on the consistency of [the pitch]. I pitched close to 50 innings and had only eight walks. I would take that pitching conventionally."

Dickey worked on varying the speed of the knuckleball and would pitch according to the situation. His range ran the gamut from 61 to 81 mph, and the movement of the ball depended on the speed of the pitch.

"The harder one doesn't flutter as much," he said. "It will break sharp and late, but which direction I don't know, which makes it a good pitch. If I don't know where it's going, [the hitter] doesn't know either. The slower one will break three or four times before it reaches the plate."

He wants to take his expanded repertoire to the next level.

"I felt I had a real mission when I went down there," he said of the April demotion, "and figured if I could be consistent, it would only be a matter of time before I came back here with this team or someone else. I just want to stick to my business and do my best. I'm anxious to get started."

He can always sleep later.