Darren Ferguson said he had no choice but to take off James Coppinger in Doncaster Rovers' defeat at neighbours Rotherham United.
Coppinger was replaced by Jordan Houghton early in stoppage time with Ferguson explaining the veteran midfielder was suffering from cramp.
"I had to take Copps off because we was cramping up," Ferguson said.
"I didn't want to because he was our best player.
"He was outstanding, his composure on the ball every time he got on it he looked after it.
"He was giving them a problem but I had to take him off.
"I won't use the word he used but he was shattered."
Rovers suffered two considerable injury blows at the New York Stadium with Tom Anderson and Alfie Beestin both requiring lengthy treatment and being stretchered off.
Anderson was involved in a heavy clash with goalkeeper Marko Marosi and suffered a head injury while Beestin damaged his ankle in a 50-50 challenge with Rotherham's Richard Wood.
Ferguson said: "I don't know if Tom was knocked out.
"The way he has fallen, there was no support for his head or his neck.
"It didn't look very good I have to say.
"Beestin is a bad one. I think it looks like his ankle.
"You would imagine it was some sort of ligament damage.
"That wasn't a foul, it was a good strong tackle from the boy. I wasn't complaining about that at the time, it was more about the linesman not giving us a corner."