Manchester United manager Jose Mourinho has revealed they do not yet know the extent of his injury after he was forced off against Real Madrid.
Herrera was one of eight substitutions introduced at half-time but lasted just six minutes following a heavy challenge from Madrid midfielder Oscar, report the Manchester Evening News.
Juan Mata was forced off at Real Salt Lake last week and could be fit to face Barcelona on Wednesday but Herrera is a doubt for United’s final pre-season fixture in the United States.
United flew to the capital city straight after their shootout win over Madrid on Sunday and Jose Mourinho was asked about the extent of Herrera’s knock.
“At least very painful,” Mourinho said when asked about the extent of Herrera’s knock. “Because for Ander to come out it has to be very painful.
“I want to wait and see what it is but I say to the players no risk in friendly matches. If you feel something, if you feel that something is coming, sometimes a little muscular injury, get out, the result is not important.
“But he was very painful, it was in front of the bench, I think, it was a bad contact, maybe ribs, I don’t know, maybe muscle, I don’t know.”
The official attendance was announced as 65,109 but the spectacular Levi’s Stadium was pockmarked by thousands of empty seats and Mourinho questioned the timing of the game and felt Cristiano Ronaldo’s absence contributed.
“I don’t know what to say, is Sunday the best day, for a family holiday in July?” he asked rhetorically. “The price of tickets, I don’t know, Ronaldo not here, I don’t know what to say.
“I say that I think the people enjoyed and a penalty shootout is something very American, they like this kind of decision, so I think it was not bad for the crowd.”