Christian Pulisic will have to undergo a scan to assess an injury sustained during the warm-up ahead of Chelsea's 3-0 win over Burnley, Frank Lampard has confirmed.
Timo Werner was drafted into the starting line-up after Pulisic, who scored a hat-trick in the corresponding fixture last season, tweaked his hamstring prior to kick-off on Saturday.
Chelsea were unfazed by the United States international's absence, with Hakim Ziyech netting the opener to become their first player since Diego Costa in 2014 to score in each of his first two starts in all competitions.
Kurt Zouma powered in his third Premier League goal of the season – already a career-best tally – before Ziyech teed up Werner to round off the scoring with 20 minutes remaining.
The injury to Pulisic, who came on as a second-half substitute in the 4-0 win over Krasnodar on Wednesday, was the only sour note for Chelsea, but though he was confident it would not mean a long spell on the sidelines, Lampard could not give any guarantees.
"Christian had a small sensation in his hamstring. So, we had to pull him," Lampard told a news conference.
"He couldn't play the game and he felt that in part of the warm-up. We will have to scan it.
"He is frustrated as he got fit and we rested him in the week where he comes on and scores. He is so keen to do well for us but we have to scan him and see how it is, so I can’t give you a time on that."
Chelsea have now kept clean sheets in back-to-back Premier League games for the first time since October 2018 and Lampard is pleased to see his team developing positively.
"It was a very complete performance. It's a tough place to come here and play, they make it very difficult," Lampard added.
"You know you have to defend your box well, you have to be very strong with the first and second balls. I wanted that to be one focus and the other to be to keep developing the way we play on the ball.
"That is what really pleased me today. Some of the passing and the movement in the team was very good. It feels like a nice step forward.
"I keep talking about the work we need to do, we are nowhere near the end of the road with that, so the performance was a really solid win. Certainly we have had good momentum from this week.
"I'm not going to jump and up and down after a win like this, but it was a really positive day."
Burnley failed to register a single shot on target against the Blues but Sean Dyche was frustrated his team were not awarded a penalty when Edouard Mendy and Ashley Barnes collided in the fifth minute.
"I think we started well. We should have had a penalty, but we know our record with penalties – I don't know what penalties are or aren't any more. I'm not remotely saying that would win us the game, but it would have given us a chance," said Dyche.
The Clarets have been awarded five penalties in the Premier League since the start of the 2017-18 season, the fewest of any ever-present team in that time.
He continued: "We're getting punished for everything. That's how it is, things go against you or feel like they're going against you.
"It's a challenge. The feeling that winning brings, the confidence it brings, it adds to what you're trying to achieve. There has to be a bit of realism – playing against these sides, top six sides, they can punish you, and they punished us today.
"I don't panic in general, to be honest. I don't think panicking will change anything. I think structure, organisation and hard work, that may change things."