Dontrelle Willis left after 2 2/3 innings with left arm soreness. (Getty)

CINCINNATI -- Reds starter Dontrelle Willis left Sunday's game at Great American Ball Park with what he called soreness in his left forearm.

Before exiting with two runners on and two out in the third inning, the Padres had scored four times on their way to a 7-3 victory that snapped Cincinnati's modest four-game winning streak.

Reds manager Dusty Baker said Willis will be evaluated again by team physician Dr. Tim Kremchek on Monday's off-day before the Reds embark on a nine-game road trip to Washington, Pittsburgh and Miami. But Willis said after the game that he thinks rest is the elixir for the injury.

"I felt some discomfort warming up and I told [pitching coach] Bryan [Price] that I wasn't feeling too good," the veteran left-hander said. "I was ready to go out there and compete. Obviously you're not going to feel 100 percent every time you start, but today I didn't have enough to go out there and win us a ballgame."

In the top of the third, Willis walked two and uncorked two wild pitches. He also was touched for RBI singles by Logan Forsythe and James Darnell. Baker and trainer Paul Lessard went to the mound after the Darnell single and Willis left the game. Sam LeCure replaced Willis to record the final out.

Up until Sunday's loss, the veteran left-hander had thrown well of late, but his ERA jumped more than half a run to 4.08. At 0-3, he hasn't won in more than 14 months -- his last victory coming for the D-backs over the Rockies at Chase Field on June 5, 2010. He's made seven starts for the Reds since being recalled from the Minor Leagues on July 10.

As recently as this past Tuesday night, Willis was in vintage form, recording his first eight-inning and 10-strikeout performance in four years. He allowed five hits and struck out 10 in a 3-2 loss.

Willis is scheduled to start again next Saturday against the Pirates in Pittsburgh.

"It was unfortunate, but the good thing is that it doesn't feel too life-threatening," Willis said about the injury. "Thank God we have the off-day. I can take a couple of days away from baseball. And hopefully I'll make my next start."