Manchester United are hopeful David de Gea's injury is not serious but Liverpool's visit to Old Trafford on Sunday may come too soon for the goalkeeper, sources have told ESPN FC.
De Gea was forced off during Spain's Euro 2020 qualifier with Sweden on Tuesday night because of an abductor problem.
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He has been in touch with United goalkeeper coach Richard Hartis and is due back at Carrington on Wednesday for tests.
Initial reports from Spain's medical staff have indicated the injury should not keep the 28-year-old out long-term but with just three days before the clash with Liverpool, manager Ole Gunnar Solskjaer may still be forced to to pick No.2 Sergio Romero.
De Gea has not missed a Premier League game since May 2018. Romero has started twice this season against Astana in the Europa League and Rochdale in the Carabao Cup.
De Gea had been superb in Tuesday's match until Marcus Berg nodded home the opener from close range in the 51st minute. Shortly afterwards the 28-year-old keeper sat down on the pitch before being replaced by Kepa Arrizabalaga.
The game finished 1-1 after substitute Rodrigo cancelled out Berg's strike with a stoppage-time goal, allowing La Roja to punch their ticket for Euro 2020.
Spain manager Robert Moreno said after the match that De Gea tried to play through the pain before being removed.
"He had pain in the abductor muscle but he received treatment at halftime and wanted to keep playing," Moreno said. "He gave us his word, but in the end he couldn't continue."
Moreno praised De Gea's performance but seemed to suggest that the starting spot could be a battle moving forward.
"If there is a debate at goalkeeper, you will be entertained because there will continue to be a debate," Moreno said in a post-game news conference.
"Aside from De Gea, others have done well. The goalkeeper is there to make stops and I'm happy that he made the stops he did," Moreno added. "De Gea is an [accomplished player]. We're proud to have three goalkeepers of such high level."
Information from Reuters was used in this report