Sweeney made contact with the center field wall at Safeco Field on Saturday while making a running catch and left the game shortly after. He did not hit the wall hard, but he immediately grimaced and placed his hand over his ribcage after making the play. Cubs manager Dale Sveum originally said Sweeney would be day-to-day.
The Cubs will miss Sweeney's bat and versatility. The 27-year-old outfielder has been a pleasant surprise for the club through the first three months after bouncing around with Oakland and Boston, batting .295 with four home runs, 15 RBI and a .869 OPS over the course of 44 games. He played all three outfield positions with most of his time coming in center.
Assuming there are no setbacks in his recovery, Sweeney will return around the middle of August. A minor league rehab stint will likely be needed before he returns to Chicago.
The Cubs will announce a roster move on Monday to replace Sweeney on the roster.