A 1-0 win at Old Trafford was an ideal result for Barcelona, but Lionel Messi was hit in the face by Chris Smalling in the first half and, as well as some bleeding, he has suffered a bruise that could give the Catalans cause for concern.
Ernesto Valverde admitted that he is yet to discover the full extent of the the issue, but that this would be learned on Thursday.
"Messi wasn't so comfortable after the blow," Valverde revealed after the match.
"We have to examine him tomorrow to see how he is.
"He was strong, but he has quite a significant bruise."
Before Wednesday, Barcelona had never won at Old Trafford and Valverde reflected on this.
"When you see the atmosphere here and the team they have and it being the Champions League, it's hard to win here," he said.
"It was a difficult game and complicated at times, but we had the clearest chances."
Luis Suarez thought he had ended his long drought away from home in Europe, but a slight touch off Luke Shaw saw the goal attributed to the defender.
"They'll keep asking me about Suarez then," Valverde bemoaned.
"The value of what he does doesn't depend on whether or not he scores, but what he generates."