White Sox designated hitter Jim Thome was placed on the 15-day disabled list Sunday with a strained muscle in his right rib cage. The move is retroactive to Saturday, one day after Thome aggravated the injury in his first at-bat against the Angels. The lefthanded slugger fouled off a pitch in the first inning and left the contest. Thome, who suffered the injury against Kansas City on Monday, had gotten off to a hot start this season, batting .340 with five home runs and 12 RBI. The 36-year-old leads the American League in walks (25) and on-base percentage (.553) and is second in slugging percentage (.680).