The Chicago White Sox suffered another blow Wednesday when an MRI revealed that Jake Peavy suffered a non-displaced rib fracture on his left side and will be shut down from four to six weeks.

Only rest was prescribed for Peavy, who will be evaluated throughout the healing process.

The announcement was made during the seventh inning of the Sox's game at Seattle, where the Sox are trying to snap a season-high eight-game losing streak.

Peavy, 32, who is 6-4 with a 4.30 ERA in 11 starts, was pulled after feeling acute, sharp pain after throwing only 2 1/3 innings against the Mariners. He struck none and allowed seven hits.

With the Sox sliding further away from contention in the American League Central, Peavy might not heal in time before the July 31 trading deadline. That wouldn't help the Sox's chances of retooling the roster or even making a late run in division play.

Left-hander Hector Santiago, who pitched two-thirds of a scoreless inning in the sixth inning of Wednesday's game, will likely take Peavy's place in the rotation. Santiago would become the Sox's fourth left-hander in the rotation.

Meanwhile, this marks another setback in Peavy's tenure with the Sox. He made only three starts in 2009 after being traded from San Diego because of a damage ligament in his ankle. On July 6, 2010, Peavy suffered a detached latissmus dorsi muscle near his right shoulder and didn't return for 10 months.

Peavy missed a start on May 2 because of back spasms.