ST. LOUIS -- When Jon Lieber takes the mound on Wednesday, it'll be his first start since June 20, and his first for the Cubs since Aug. 1, 2002.

The right-hander will replace Rich Hill, who was optioned to Triple-A Iowa on Saturday. It's not exactly how Lieber wanted to return to the rotation.

"Whatever the club needs me to do, I'm willing to do it," he said Sunday. "It's an unfortunate thing to me because I think Rich Hill is a Major League pitcher. Right now, it's command issues. He'll be back up here soon. I want to see him back up here soon. We need him to be where he needs to be to help us win."

Don't expect a complete game from Lieber against the Cincinnati Reds on Wednesday. His longest outing so far has been 4 1/3 innings. His last start was June 20 at Cleveland, when he went 5 1/3 for Philadelphia, but that season ended prematurely because of foot problems.

He's healthy this season, and has appeared in nine games in relief, totaling 19 1/3 innings, and has an impressive 1.86 ERA.

"It'll be a progression," Lieber said. "They're probably looking 70, 80 pitches. At least I should be able to get to the fifth, sixth inning.

"If I can keep my pitch counts down, the longer I can go out there," he said.

When the Phillies told Lieber he would be a reliever last season, it caught him by surprise. This year has been an easier adjustment.

"It just took about a week or two of adjusting, but it was fine," he said about this season. "Somebody asked what's the difference, and I said, 'You just never know when you're going to pitch in the bullpen, as opposed to starting every fifth day.'"

"Last year, I didn't take it very well," he said of relieving. "I approached it the wrong way. I don't think I gave it a fair chance like I should have. I knew going into this year it was a possibility. I wasn't going to take anything for granted. I was prepared for it this year, more mentally than anything."

Lieber doesn't know how long he'll stay in the Chicago rotation. He's hoping Hill pushes him out.

"I want to see Rich Hill back up here," he said.