Worried David de Gea compared Victor Lindelof's medical issue during Manchester United's victory over Norwich to that of Christian Eriksen and Sergio Aguero.
But manager Ralf Rangnick says he "seems to be OK" despite the scare.
With the score tied at 0-0 in the second half, Sweden defender Lindelof sparked worry when he abruptly stopped, seemingly under no contact, and dropped to his haunches
Midfielder Fred signalled for a substitution immediately while De Gea came well out of his goal to check on his teammate.
Lindelof was then seen pointing to his chest when speaking to the club's medical staff.
The decision was made to take him off and Cristiano Ronaldo 's penalty later sealed a win for United.
But it was Lindelof's condition that dominated the post-match conversation as De Gea faced up to the press.
Understandably flustered, he spoke to Sky Sports and compared Lindelof's condition to footballers who have recently suffered from high-profile heart problems, like Eriksen and Aguero.
He said: "Especially when we've seen some players who are feeling a bit (unwell).
"I don't know what was going on but it was like he was feeling his breathing, I don't know.
"We've already seen Eriksen, Aguero, so sometimes it's difficult to see your player acting like this. It was better to change.
"I hope he's completely fine.
"It was like breathing, difficulty breathing, he was feeling something strange so the game, the football doesn't matter, it's life, it's to be safe."
Rangnick however reassured worried fans that he has checked on Lindelof and he seems to be doing fine.
"He had a collision," the interim boss added. "He can't even remember what it was but he was struggling to breathe.
"He felt pain in his chest but right now they've checked him, they did all the tests and everything seems to be OK."
United won the match 1-0 and move up to fifth in the English Premier League.
