CHICAGO -- Cubs outfielder Alfonso Soriano underwent an MRI Tuesday night to determine the extent of the injury on his right calf, which forced him out of the game after the first inning.

Soriano ran to catch Ken Griffey Jr.'s fly ball in left-center field with two outs in the Cincinnati first, doing his trademark hop before catching it. As he came down to land, Soriano couldn't put any weight on his right leg, and hopped a few times on his left leg. Shortstop Ryan Theriot helped the outfielder as he hobbled off the field.

"As he was catching the ball, he goes up after it, and he just strained his calf," Cubs manager Lou Piniella said. "It's his unique style."

Piniella didn't want to project how long Soriano would be sidelined until he got the test results Wednesday.

"Let's get the results tomorrow," Piniella said. "If he's out for an extended period of time, it'll hurt us."

If Soriano has to go on the disabled list, one option for the Cubs would be to call up outfielder Matt Murton from Triple-A Iowa. Assistant general manager Randy Bush was with the Iowa Cubs on Tuesday night.

Soriano missed time in April 2007 because of a sore left hamstring, injured nearly one year ago to the day on April 16, and suffered a more serious injury to his right quad last August.

Mike Fontenot pinch-hit for Soriano in the first inning, and Mark DeRosa moved to left field.

Soriano had gotten off to a slow start and was batting .175, with two homers, five RBIs and two stolen bases. Last September as the Cubs' leadoff man, he hit .320 with 14 homers and 27 RBIs.