Morel was on a rehabilitation assignment with Triple-A Charlotte when he re-aggravated the area in a game at Toledo.
"He left the game last night and pulled himself out of the game," White Sox manager Robin Ventura said. "He is on his way back here to get checked out. Something else is going on their so it is a setback."
Morel has had lower-back issues since early March and never got his offense going before going on the DL on May 18 with lower a lower-lumbar strain. Morel was 8 for 30 in his stint with Charlotte.
Morel is hitting .177 this season with no homers and 5 RBIs.