TORONTO -- The season may not even be a month old, but for Carlos Guillen it must feel like the dog days of summer have already arrived.

Through just 18 games this season, Detroit's first baseman has suffered through what seems like a season's worth of leg injuries.

First it was a right hamstring muscle that he tweaked while running to first base on April 11 against the White Sox. In case that wasn't enough pain to deal with, on Friday night in Toronto, Guillen fouled two consecutive pitches off his left leg.

The first ricocheted off a protective brace on his lower left leg and didn't cause much damage. He wasn't quite as fortunate with the second, which hit Guillen a few inches below the knee cap on the inner part of his lower leg.

The force of that ball nearly sent Guillen to the ground, but he remained in the game to finish his at-bat. Despite the tough at-bat, the gritty veteran was at the ballpark on Saturday morning at 9 a.m., arriving for another day of work.

Tigers manager Jim Leyland said he didn't expect anything else from a guy such as Guillen, and that's the difference between playing hurt and being injured.

"He was out there and I asked, 'How are you doing?' And he said, 'Fine,'" Leyland said. "He's hurting, but he plays. He's tough."

Guillen estimated that it was at least the eighth time he has fouled a ball off his leg this season. He doesn't have much of a reason why it keeps happening other than perhaps it's his mechanics.

"I don't know why -- it's just my swing," Guillen said. "[Earlier this season] in Chicago I did it twice, one hitting left-handed and right-handed, too."

Despite the injuries, Guillen has played in all but two of the Tigers' games this year. His presence is critical for his club's offense: Entering Saturday's action he led the Tigers' everyday players with a .352 average and three home runs, while contributing six RBIs.

Guillen was deemed ready to play on Saturday, but Leyland did unveil three changes to his starting lineup for the second game of a four-game series against Toronto.

As expected, second baseman Placido Polanco received the day off to rest a sore left hip flexor that has been causing him pain in his lower back. In his place was utility infielder Ryan Raburn.

Joining Polanco on the bench were left fielder Marcus Thames and utility man Brandon Inge, who has been seeing a lot of action in center field with Curtis Granderson on the 15-day disabled list with a fractured middle finger on his right hand.

Clete Thomas got the start in center field and batted leadoff while Jacque Jones got the start in left field after receiving the day off on Friday night.