Gonzalo Higuain risks a Champions League ban after he was spotted making a lewd gesture at Barcelona fans during the Juventus defeat.
He was jeered when substituted late on at Camp Nou in the 3-0 loss on Tuesday evening.
As he walked back to the bench, Pipita was caught on camera holding up his middle finger to the crowd.
UEFA could take a hard line against the Argentina international, because this has been punished before.
Roberto Mancini was given a one-match Serie A ban for that same gesture, while Luis Suarez was suspended when doing that for Liverpool against Fulham.