"It's not going to be the first time I'm going to play first base in the game," he pointed out Wednesday. "I feel comfortable."
Sean Casey's left calf injury puts Guillen in a spot where he has to switch positions, but it's something the Tigers knew could happen. Manager Jim Leyland decided in the final days of the regular season to leave Chris Shelton off the postseason roster, making Casey the only natural first baseman available and Guillen the backup in case of a late-inning switch or for injury.
Now that they're in the scenario, Guillen will reprise his World Baseball Classic role as a regular first baseman. He may or may not have the eyes of Venezuela on him this time, but he'll certainly have the eyes of Detroit.
"What happens is you just improvise when you get in situations like this," Leyland said. "We'll do what we have to do. Is it an ideal situation? No, it's not. But I remind everybody that the Oakland A's just lost their double-play combination, so we're certainly not looking for any sympathy."
Guillen, for one, isn't expecting it. His time at first base began over the winter, when he played there for a brief stint in the Venezuelan Winter League. He showed enough skill doing it in the Classic that Leyland made him an option at first base along with Ivan Rodriguez once the Tigers lost Dmitri Young to the disabled list.
Guillen made four starts at first base in the regular season and four more late-inning appearances. Though Guillen made 28 errors at shortstop this year, his error on Jason Kendall's ground ball Tuesday was his first as a big-league first baseman.
The main difference shifting over, Guillen said, is obvious.
"It's the angles," he said. "You know, it's important to be on time on the base when the hitter hits a ground ball somewhere in the infield. To me, it's easy.
"I don't feel it's hard. Shortstop is hard. When you play shortstop, you can play everywhere."
What Guillen lacks in experience at first base, he makes up for in range. As a shortstop, Guillen can range into the hole more easily than Shelton or with Casey. In return, first base is a way to ease the workload on Guillen, whom Leyland said is dealing with a sore hamstring.
"I think he's pretty beat up right now," Leyland said. "I think what you see at this time of year is everybody's beat up. It's just a matter of doing the best you can."
Short-term, Guillen is a way to fill in the hole. Long-term, first base could be a way to extend Guillen's career as age and wear-and-tear take their toll on his knees.
No help: Unlike the regular season, there's no disabled list in the playoffs, and players can't be called up in the middle of the series. Thus, even though Shelton is with the team and working out, the earliest he could play would be Game 1 of the World Series if the Tigers advance.
Leyland wasn't looking for pity, but he was looking to understand the reasoning behind the Major League rule that allows no injury moves under any circumstances.
"No, I don't understand the logic," he said when asked. "I'm sure it was [exploited] by some club, but I don't understand the logic. Because in my opinion, I can understand some of the thought process, but I can't understand when Major League Baseball representatives are there, the head of the umpires is here, a great percentage of the country is watching the game. So if a guy slid into home plate and broke his angle, I would think they would have enough sense to say that's a legitimate injury.
"Now, did people tinker with it? Yes, they probably did, and that's what caused this. And I'm not complaining, because the rule's fair for everybody and it's the same for everybody. But I just say I think there are instances where you have to use common sense."
Gomez gives it a go: Neifi Perez's start at short wasn't the only lineup change Wednesday. Leyland gave Alexis Gomez a start at designated hitter over Marcus Thames in order to get another left-handed bat against Esteban Loaiza, who gave up a .319 average to lefties in the regular season compared to .265 to right-handers.
It was the first playing time of any sort in the postseason for Gomez, who made the playoff roster as an extra outfielder after splitting the year between Detroit and Triple-A Toledo.
Jason Beck is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.