Christian Pulisic gave Chelsea a boost ahead of their quarter-final Champions League tie against Porto after he emerged for training on Tuesday morning.
The open training session saw the Blues train in front of the cameras and the American appeared with the rest of his Chelsea teammates, which could suggest the hamstring injury was minor and precautionary.
Chelsea are preparing for the first leg as they travel to Seville to face the Portuguese side on Wednesday due to COVID-19 travel restrictions and regulations.
Training took place before Thomas Tuchel's pre-Porto press conference on Tuesday morning, where he is expected to provide a further update on the fitness and availability of the American.
The 22-year-old was taken off at half-time during Chelsea's 5-2 defeat to West Brom in the Premier League on Saturday after tweaking his hamstring, which forced Tuchel into a change at the interval.
Tuchel confirmed the bad news post-match saying, "Christian was injured. So he had to be substituted. He felt his hamstring when he went out for the second half and he said he couldn’t continue.
"We hope it isn’t too bad, because initially he thought it would be fine but when he went out for the second half, he felt some pain and he said he couldn’t risk it. I hope it’s not a bad injury but just a little problem."
Pulisic is hoping the Blues can bounce back straight away on Wednesday night.
He added: "It’s a big test of our mentality now. We’ve got some really big games coming up.
"We’ve been in good form prior to the international break and obviously we’ve come back and lost one game. We can’t dwell on that because we have a lot to play for in both the Premier League and the Champions League.
"We have to recharge now, refocus and regroup and come back strong and ready for the next game."