Victor Lindelof is wearing a heart monitor as doctors look to determine the reason for the Manchester United defender's chest pains during Saturday's Premier League clash with Norwich City.
The Sweden international was forced off the field during his side's 1-0 win after appearing to have difficulty breathing at Carrow Road.
Man United have since issued a statement confirming that the centre-back has "recovered well" from the incident, with the club also ruling out coronavirus as the cause.
However, Lindelof's wife Maja Nilsson Lindelof has said that her husband is currently wearing a heart monitor and undergoing tests to potentially determine the cause of his problems.
"It was a scary match to watch and Victor was very cut up afterwards. Yesterday he did a lot of tests and has a heart monitor on for two days to make sure everything is OK," Maja wrote on her blog for Elle.
"[It was] Incredibly uncomfortable, especially when I did not get hold of him, which I always manage to. It was a long time before I got hold of someone on the team who updated me. Everything seems to be OK as luck would have it and we are waiting for answers to the last tests that will end tomorrow."
A coronavirus outbreak at Man United, which emerged on Sunday, has led to Tuesday's Premier League clash with Brentford being postponed.