CHICAGO -- Like he has so many other days over the last couple years, Tigers manager Jim Leyland put Carlos Guillen into his starting lineup at shortstop for Friday night's game against the White Sox. Once this series and this season wraps up, he'll be writing in Guillen somewhere else.

The Guillen experiment at first base is about to become a full-time job. Leyland confirmed the move first in an interview with WJR Radio on Friday morning, then with reporters in the afternoon. And Guillen, who didn't sound like a big fan of the idea a week ago, is now on board with the move.

"I enjoy playing every day," Guillen said. "I don't enjoy sitting on the bench or in the training room."

That, in effect, was the reasoning Leyland used when he discussed the shift with Guillen on Wednesday in Detroit. It was, as Leyland put it, "about as good a conversation as you can have about it."

And the talk revolved around Leyland's belief that playing first base gets the most out of Guillen's skills.

"We signed this guy [in March] because we think he's a great player," Leyland said. "He'll be a great player wherever he plays. We've got him for four more years. I want to make sure he can play.

"I think the biggest thing as far as I'm concerned is I'll have him on the field all the time. Because I think [first base] is a lot less stress."

Guillen has already eased into the role. He has essentially split time between shortstop and first base over the past couple months, ever since the club called up Ramon Santiago. That hasn't happened as often down the stretch, ever since the Indians swept the Tigers out of the playoff picture last week. He hasn't started at first base since that series, though he has moved there for the late innings three times since.

Near the end of that Cleveland series, Guillen was cool to the notion of playing first base full-time when discussing it with reporters, saying it wasn't really as easy on his knees as many would believe. He'd do it to help the team, he said, but he cautioned the Tigers had better get a good shortstop to take his place. Though the Tigers had brought up the possibility when they signed him to his four-year, $48 million contract at the end of March, he expected that to come near the end of his contract, not the beginning.

His talk with Leyland, he said, assuaged some concerns.

"I know it's going to be a good [shortstop]," Guillen said. "I don't know who it's going to be."

He also said he wasn't trying to change Leyland's mind when they talked.

"It's OK," he said. "I don't have any problem. I just want to help this team get better."

How the Tigers replace Guillen at shortstop will determine how good they will be. Leyland isn't sure how they're going to do that quite yet.

In the same interview with WJR, Leyland said they would probably look to add a shortstop via trade or free agency, but downplayed the much-rumored possibility of acquiring Jack Wilson from Pittsburgh. The Pirates also hold a $5.85 million option on Cesar Izturis, which they could pick up to try to deal him.

The big potential name on the trade market would be Edgar Renteria, whom the Braves could deal for pitching help if they decide to move young Yunel Escobar to short. Acquiring him, however, would likely require a pitcher currently in the big leagues rather than just prospects.

The list of prospective free agents starts with David Eckstein and Omar Vizquel and continues with Juan Uribe.

Sheff to sit this weekend: After Gary Sheffield went 0-for-4 with three strikeouts Friday night, Leyland said he planned on resting Sheffield for the final two games of the season.

"He's hurting," Leyland said.

It's not anything much different than he has been feeling the last several weeks, Sheffield said, but Friday's game was an example of the struggles Sheffield has encountered down the stretch.

As far as solving his shoulder problem long-term, Sheffield said he expects to talk with team personnel Saturday on what his options are for taking care of the problem now that they've looked at all the MRI and x-ray exam results. He would like to rehab the injury without surgery, but he also believes he could undergo a procedure to shave bone off of the shoulder.

Bonds unlikely for Detroit: Leyland was also asked in the WJR interview about the possibility of signing Barry Bonds, who will be a free agent at season's end.

"That will not happen," he said of a signing. "It's simple, really. We have Gary Sheffield in that role, so we basically have our DH in place. And by his own admission, I think it's very difficult for Barry to go to the outfield anymore. I know Sheffield said he would go to the outfield, but he's had some injuries of his own. I don't think that would work out.

"I think it's a nice thought. I think it was probably a common factor for the people because of my relationship with Barry. And don't get me wrong, I'm not saying I wouldn't like to have him. I'm not saying he wouldn't be able to do a good job for us, but I don't really think that's a fit for us."

Coaches coming back: Not surprisingly, the Tigers announced Friday that Leyland's entire coaching staff will return next season. The only one who was in doubt was first-base coach Andy Van Slyke, whom Leyland said was considering a move to manage in the Minor Leagues somewhere to gain experience.

"He'd been contemplating managing. He wants to manage," Leyland said. "And if he wants to manage, at some point, he has to go manage. He was asked back, so he had the choice of coming back or going to go manage. And at some point, that's what he should do.

"I wanted him back bad. He's done a tremendous job. But at some point, if you want to go manage, you have to go manage."

Coming up: Justin Verlander (18-6, 3.68 ERA) has a chance to become the 10th Tiger in the past 35 years to win 19 games when he takes the mound Saturday for his final start of the season. Gavin Floyd (1-5, 5.71) is scheduled to start for the White Sox in the 7:05 p.m. ET start.