DETROIT -- Gary Sheffield wanted to get his shoulder right in time for the stretch run. To do it, he had to go back to offseason training.

For over a decade, Sheffield estimates, the Tigers slugger has spent at least part of his offseasons working out in Tampa, Fla., with trainer Larry Mayol -- or as Sheffield calls him, "Military Larry." He doesn't pick up a bat the entire time, because Mayol has him focusing on his physical shape rather than his swing.

When Sheffield needed to work his shoulder into shape, he went back to St. Petersburg, Fla. and to Mayol. On Tuesday, he returned to Detroit and said he's ready to rejoin the lineup when he's eligible to be activated from the disabled list on Thursday.

"I know it's a lot better," Sheffield said of his shoulder. "To what degree, I can't say, but I know when I picked up the bat this last time, I felt a lot better than I did coming back before."

In his estimation, it's the best he has felt since he jammed his shoulder on a play in the outfield in July. If he's back, it's the best feeling the Tigers could hope for in their attempt at a September run back into the playoffs.

"If he can hit," manager Jim Leyland said, "he's going to be in the lineup. You can take that to the bank."

The shoulder has bothered Sheffield to some degree for most of the summer, but had been more pronounced over the last month and a half. He missed two games in late July to have a cortisone shot, then was knocked out for a week in early August once he started feeling numbness in his hands and continued soreness.

He went 10-for-51 with eight strikeouts upon his return because the shoulder wouldn't allow him to keep his right hand on the bat while following through on his swing. Eventually deciding he was hurting the team, he decided to try to get the shoulder right once and for all.

For about a week, he worked out for close to four hours a day with Mayol, whom Sheffield knew as a kid when he was working out with his uncle, Dwight Gooden. Together, their 8 a.m. workouts focused on strengthening the shoulder and improving the range of motion.

"Once I was able to do the exercises, we were able to get a little more strength in there, it seemed like the clicking [sensation in the shoulder] went down a little bit," Sheffield said. "Each day went by and I was able to do more. When I got to the point where I had my normal strength, that's when I picked up the bat and started swinging. The first couple swings, I noticed the difference. I was able to finish my swing."

When he left Detroit, the goal was to improve his shoulder to the point where if he still needed one last cortisone shot, it would get the shoulder to 100 percent strength. Now, he said, "I don't think I'm going to need it.

"That was the goal, just to get to a point where I don't need it, just in case something else goes wrong later on and I need it. The way it feels now, I don't see any problem later on. I've put in my work and got it to the point where I needed it, I think."

He's also optimistic that with the exercises, he won't need offseason surgery, an option he had discussed last homestand. He'll have to work out his shoulder the rest of the season to tune up his shoulder muscles for activity, but the workouts won't be nearly as long. They'll essentially replace the shoulder work Sheffield used to get by playing and throwing in the outfield in past years, before he became Detroit's designated hitter.

Because Sheffield usually doesn't swing a bat in the offseason until he gets to Spring Training, he doesn't think he'll need a lot of swings to get his timing back, only a long at-bat or two to see some pitches. So even without a rehab assignment, he's optimistic he can make an immediate impact, just in time for the Tigers to welcome the AL Wild Card-contending Mariners to town on their stretch run.

"That's what I'm here for," Sheffield said Tuesday, "and that's what I'm looking at. I'm not looking [at it] like I have to be the savior. Like I said before, this team is good already. I just have to do what I'm capable of doing and what I've always done. And if I can do that, hopefully it improves this ballclub."

If he's healthy, an improvement shouldn't be a question. Though the Tigers entered Tuesday batting .290 as a team in Sheffield's absence, five points above their average for the season, they've struggled to fill the void in the third spot in the lineup, starting Marcus Thames, Sean Casey, Timo Perez and Ryan Raburn there. They combined to bat .246 with one home run and seven RBIs over 12 games in the third spot entering Tuesday.

Now batting third: Tuesday was Omar Infante's turn to bat third at DH, mainly because he entered the night 15-for-35 lifetime against White Sox starter Jon Garland. It was enough to earn Infante his first game action since being recalled from Triple-A Toledo last Saturday.

With an expanded September roster and an offense looking to heat up, Leyland indicated he could play the matchups quite a bit in deciding spot starts down the stretch.

"I'm not a big fan of [expanded rosters], but it allows you to pinch-run, pinch-hit, do some things you normally can't do when you're sitting there with four extra players," Leyland said. "This time of year gives you a little more flexibility."

Infante started at DH over Magglio Ordonez, Leyland said, because Ordonez preferred playing in the outfield despite his sore right foot. However, the foot felt worse as the game went on, and Leyland said afterwards that he'd likely give Ordonez the game off for Wednesday.

Coming up: Kenny Rogers (3-2, 5.23) returns from the DL to make his first start in over a month when he takes on the White Sox, the same team he faced in his last start back in July. Gavin Floyd (1-2, 6.92) is slated to pitch for Chicago in the 7:05 p.m. ET start at Comerica Park.