De Gea, who was replaced by Chelsea’s Kepa Arrizabalaga, was able to walk off the pitch but his involvement in Sunday’s Premier League clash at Old Trafford was nevertheless cast into doubt.
Robert Moreno, Spain’s head coach, said after the final whistle that De Gea had suffered the injury during the first half and attempted to play on.
“It’s a pity for him,” Moreno added. ”It’s a pull in his adductor muscle and we’ll have to see what the extent of the damage is.”
If De Gea is unavailable for the visit of Liverpool, United manager Ole Gunnar Solskjaer is likely to turn to back-up goalkeeper Sergio Romero.
Romero played in United’s narrow EFL Cup and Europa League victories over Rochdale and Astana respectively but the Argentine’s last league appearance came back in May 2018.
De Gea joins a long list of injured players at United, with Paul Pogba, Anthony Martial, Aaron Wan-Bissaka, Jesse Lingard and Victor Lindelof all missing games before the October international break.
Luke Shaw, Phil Jones, Mason Greenwood and Diogo Dalot have also been sidelined of late, though Solskjaer will hope to have several players back in time for Sunday.