The centre-back was withdrawn after 56 minutes of the 2-1 defeat at Stamford Bridge and will now require further assessment to determine the severity of the issue.
Slot explained in his post-match press conference: “I don’t know if it is a big injury, but what I do know is he limped a little bit and when I asked him he said he felt his quad a little bit.
“Then, for me, all alarm bells go off because in another sprint you never know if that is going to go good.
“It was also already a substitution I had in mind, maybe for a few minutes or a little bit later, because the right centre-back had a lot of ball possession and we needed to create from that position. We all know Ryan [Gravenberch] is quite good in that.
“It might be OK that he went off early enough but it was clear I had to take him off because he was limping.”