CHICAGO -- An MRI showed no damage to John Grabow's left knee and the Cubs reliever received a cortisone shot Saturday.

Grabow, who last pitched Friday in Cincinnati, giving up three runs on four hits over one inning, had an exam on Saturday. He threw on the side Monday and Lou Piniella said he'd like to give the lefty at least one more day if possible.

"It's something I've been pitching through for a while," Grabow said. "It's been bothering me for a few weeks now. I tried to pitch through it and thought it would go away, but it didn't go away."

Grabow said he's never had this kind of discomfort before and wanted to treat it as soon as possible.

"He's ready to go," Piniella said of the reliever, who has a 9.26 ERA.

Lee working out of his slump

CHICAGO -- On the last road trip, Derrek Lee hit .167 and is batting .210 overall. That's not good for the No. 3 hitter in the Cubs' lineup.

"No one likes not getting hits," Lee said Monday. "We're obviously off to slow starts. We're going to turn it around."

All the first baseman needs, he said, is one swing to get realigned.

"It seems like you have that one at-bat, get that feel, and it clicks from there," Lee said.

This isn't the first time he's gotten off to a slow start. But these funks don't usually last this long.

"I try not to look at past years, to be honest, because I don't want to take anything for granted," Lee said. "You can't say, 'I did it last year' or whenever so it's going to automatically happen. You just keep working. You know the ability is there. You just have to get it done."

The Cubs aren't going to make up ground in the National League Central if the guys in the middle of the lineup, Lee and Aramis Ramirez, don't start hitting. Ramirez was batting .160 entering Monday's game against the Marlins.

"That's how we want it," Lee said of the expectations. "We're right in the middle of the order. We're the production guys. We have to get it done."

Lee does work with hitting coach Rudy Jaramillo, but trusts himself more.

"I still feel I'm my best hitting coach," Lee said. "I listen to how my body feels and I know what I need to do. Rudy's there for support. I've had this swing for a long time. I know what gets me in trouble. I get in these funks sometimes and I have to work my way out."