Marcos Alonso was in the starting lineup to face Manchester United just over a week ago, but pulled out of the game before the game started and was replaced by Kurt Zouma.
Chelsea eventually lost the game 2-0 with many believing Alonso was sorely missed.
The former Fiorentina player has revealed what really happened to him.
“I was throwing up the night before and wasn’t feeling very good,” Alonso said.
“I tried to do the warm-up the following day but I was about to faint on the pitch.
“I did not want to ask for a substitution after five minutes, so I pulled out.
“I watched the first half in the directors’ box but I had to go to the team coach to have a lie down on my own.
“I fell asleep (and missed the second half) as I was feeling so bad.
“I took a couple of days off and did not eat a lot. But I felt good against Spurs.
“I was a little bit tired in the first part of the game because it had been two weeks since I’d last played, but I’m ready for Tuesday.”