Weeks tumbled over first base while hustling out a ground ball, landing face-first in the infield dirt. The A's first selection in the 2008 First-Year Player Draft threw off his helmet in pain as the Cougars training staff rushed out to help him.
"I think it's a hip flexor, but I don't know the extent of the injury or how bad it is," Kane County manager Aaron Nieckula said after the game. "We're going to take him in for an MRI, be reevaluated tomorrow."
Weeks was eventually helped off the field to applause from the Wrigley Field fans. He was replaced by Cougars infielder Michael Richard in the bottom half of the first inning.
"It looked like it was pretty bad, but he was able to put weight on it and walked up the stairs under his own power," Nieckula said. "He's a limber guy, pretty flexible. When he hit the bag, it might have popped."
The shortstop was excited on the field before the game with the expectation that his mother and sister would be in the Wrigley Field stands. The 11th selection in the 2008 Draft, the University of Miami star made his professional debut with the Cougars on July 9. Weeks was hitting .301 with one home run and eight RBIs through his first 18 games.
Bryan Smith is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.