CHICAGO --- This development could be a big uh-oh for the Reds and pitcher Aaron Harang.

Harang was sent back to Cincinnati on Wednesday afternoon to get an MRI for his sore right forearm and be examined by medical director Dr. Tim Kremchek. Regardless of the outcome, Harang is expected to miss his next scheduled start Sunday at Milwaukee.

"We're just looking for answers. Hopefully the doctor will give us some answers," Reds manager Dusty Baker said

On Tuesday, during a 7-3 loss to the Cubs, Harang lasted only 4 1/3 innings while giving up six earned runs and setting a career-high with seven walks. His velocity seemed lower than normal, mainly in the high-80's.

Harang was originally slated to start vs. the Nationals on Saturday but was pushed back to Tuesday after he complained his forearm was stiff. The 30-year-old reported that his forearm wasn't bothering him while he pitched against the Cubs.

"I woke up at 5:30 this morning and it had stiffened up," Harang said before leaving for the airport. "Obviously it was something that didn't completely go away. I felt great yesterday warming up and playing long toss. No discomfort at all."

Harang called head trainer Mark Mann before general manager Walt Jocketty, Baker and Kremchek were notified. Last week, following a Kremchek examination, a serious ligament injury had been ruled out.

"All the stuff he did was to test the ligament," Harang said. "[Kremchek] said with everything he did, if there was something wrong with the ligament, I would have been screaming at him. He thought it was more muscle than anything. Hopefully it's just something minor that a good amount of rest will take care of. I can rehab it and strengthen it back up."

During an already trying 2008 season, Harang is 3-11 with a 4.76 ERA in 20 games, including 19 starts, over 123 innings. He is second in the National League in losses and hits (138). But he has been the ace and consistent workhorse for the rotation in recent years. A long-term injury would be a serious blow to the pitching staff.

Harang was a 16-game winner in both 2006 and 2007 and has worked at least 211 innings the previous three seasons. His only stint on the disabled list was in 2004 for a sprained ligament in his right elbow.

One has to wonder if the emergency relief appearance Harang made on May 25 is coming back to haunt him. During an 18-inning game at San Diego, the right-hander came back on two days' rest and threw four innings (63 pitches) after the bullpen was used up. Over an eight-day period, Harang pitched three times.

Before the relief outing, Harang was 2-6 with a 3.50 ERA in 11 starts. In the eight starts since, he is 1-5 with a 7.31 ERA with 63 hits allowed over 44 innings. Only two of the outings went seven innings and none lasted more than seven.

Baker didn't believe there was a connection between Harang's relief appearance and the current injury.

"No, we backed him up," Baker said. "It's been about a month or six weeks. It was going on before that, actually. Not the soreness part, just the him not being Harang part. It seems like this has affected the location of his breaking ball more than anything."

The leading candidates to replace Harang on Sunday are Triple-A Louisville's Daryl Thompson and Homer Bailey.

Thompson pitched on Tuesday for Louisville and gave up one run on six hits over six innings for a win. Thompson, who was sent back down last week, was 0-2 with a 6.91 ERA in three big league starts.

Bailey pitched six innings on Monday and allowed all four of his runs in his final inning for a loss. He struggled during his previous three-start call up and went 0-3 with an 8.76 ERA.

"Either way, we'll need somebody to take [Harang's] place," Baker said. "We haven't determined who that is yet."