Chelsea boss Thomas Tuchel has confirmed why Christian Pulisic came off during their 5-2 defeat against West Brom.
The 22-year-old came off at half-time for Mason Mount in what was a surprise change initially after he put Chelsea ahead before West Brom took a 2-1 lead at the break.
And Tuchel has provided a comment on the American's injury, saying: "Christian did a sprint when he came back out for the second half and said that he felt his hamstring would not survive the game if he continued.
"So we had to make the decision to substitute him straight away."
Pulisic took to social media post-match to express his disappointment at the defeat which takes top four out of their hands.
Chelsea next face FC Porto in the Champions League and it remains to be seen if Pulisic will be fit enough to be in contention to be involved in the quarter-final tie.
"There was nothing much in it until the red card came and after that we were not able to cope with the situation.
"I don’t know why but it was like this. We gave away two very easy goals before half-time but even in the second half what could go wrong went wrong. We have to accept a big loss today and hopefully it’s a big wake-up call for all of us, me included.
"We will get the right response because this is sport and it’s absolutely necessary. First of all, it’s important that we digest it because I did not see it coming so now we have to take our responsibilities, and shake it off and continue tomorrow."