CHICAGO -- Chicago Cubs outfielder Alfonso Soriano will undergo an MRI on Tuesday on his left hamstring, which he strained on Monday night trying to catch a ball in center.

His status was officially listed as day-to-day, but he may be sidelined for a few days.

"I feel better than when it happened," Soriano said after Monday's game, a 12-4 win over the San Diego Padres. "They gave me a lot of treatment, and I feel better on my leg."

But Soriano was limping as he left the Cubs clubhouse.

"If it's not bad, I think I'll take five, six days or maybe a week," Soriano said. "I believe it's not that bad, it's not a big deal."

Soriano dove for the ball in shallow center that was hit by Padres pitcher Clay Hensley. He thought he caught the ball, but he appeared to have trapped it.

"He made a heck of an effort on that ball," Cubs manager Lou Piniella said. "He made a really good try. I couldn't tell if he caught it or not. You can't see from the dugout."

Soriano said he hurt his leg going after the ball.

"I think after I caught the ball, I put a lot of pressure on my left side," he said. "It stretched my muscle. I tried to do the best I could in the field. I never think that's going to happen. I hope I only miss a couple days."

Piniella, who had argued in Soriano's favor for the catch, walked off the field with the outfielder, whom he'd had a chat with before the game. Soriano was batting .234 entering the game, and Piniella felt he'd been pressing, possibly trying to live up to the $136 million contract he signed in the offseason.

"We had a very good talk," Soriano said. "He's a great manager, and he tried to make me more relaxed. I told him I feel very comfortable. I've had a slow start, but it's not because I'm playing center field. It happens. It's not because I'm playing center field."

Piniella tweaked the Cubs' outfield alignment before the game, with Jacque Jones starting in left for the first time since August 2003, and Matt Murton in right for the first time in his big-league career. After Soriano exited, Jones moved to center and Cliff Floyd took over in left.