Balogun was sidelined for about two months with the injury and returned to competition at the end of November.

Balogun, who joined Monaco from Arsenal in a permanent transfer last year, was substituted after 68 minutes last week during a 2-1 loss to Marseille in the French league. Monaco coach Adi Hütter said he took a hit on his shoulder and that he has been in pain since.

“Yesterday he could not finish the practice because it was painful. He has had treatment and stayed indoors today,” Hütter told reporters on Thursday, adding that he was not sure whether the striker could recover in time for Monaco's game against Toulouse in the French league on Saturday.

Balogun was in good form earlier this season, scoring for a third straight game as Monaco won 2-1 at Rennes on Oct. 5 before leaving the match with an injury. He suffered a dislocated shoulder and the injury led him to withdraw from a couple of matches with the U.S. squad.

“For sure, he is a bit frustrated about this because he worked hard for his comeback,” Hütter. “He did a lot during his treatment and now he feels pain. Everybody crossed the fingers that he can be back maybe on Saturday.”

Balogun, born in New York and raised in London, signed a five-year contract with Monaco.

Arsenal and Monaco both have 10 points after five matches in the league phase of the revamped Champions League ahead of Wednesday's match at the Emirates.