Chelsea manager Frank Lampard is hopeful Christian Pulisic will not be kept out of action after he had to be substituted in Sunday's 1-0 win at Leicester.
Pulisic was taken off and replaced by Ruben Loftus-Cheek midway through the second half of the FA Cup quarter-final tie.
The USA international has been decisive since the Premier League's return this month and his recovery from injury, having scored in 2-1 victories over Aston Villa and Manchester City in the last week.
Lampard confirmed the 21-year-old suffered some discomfort, but is unsure if he will be available for the trip to West Ham on Wednesday.
"Christian felt a tightness in his calf in the second drinks break, hopefully nothing that keeps him out," he told reporters, adding that Andreas Christensen was missing because he "had a problem with his hip [on Saturday]".
The coach was relieved to see his side seal a place in the last four of the FA Cup, but admits their performance was not up to standard.
"The result was satisfying and getting to the semis was satisfying. We weren't our usual selves today," he said. "We were below what we usually produce. But I am happy with the result. We won the game and must learn from some of the mistakes in our game.
"I don't want to sound too down after this. You have to show the grit to get a win when you don't play well. We go on to the next one. We can park the Cup and focus on getting the league wins to be in the Champions League."
With the game still goalless at half-time, Lampard opted to take off young stars Billy Gilmour, Mason Mount and Reece James.
"It is a learning experience. I could have taken more off, or other players off," Lampard said when asked about the decision.
"I am not pulling those out on their own. They will be top players for this club and have top careers. But if I have to do something in games I will do it. It was one of those games where I had to do something. They will take it on the chin.
"We were gifting Leicester space and ease to win the ball back. We are fortunate they didn't take those chances. All thee subs, in their own way, livened up the performance."