Chelsea manager Frank Lampard has confirmed Christian Pulisic will miss Wednesday's game with Rennes, but should return by the weekend.
The American had been named in the starting XI for Saturday's Premier League game away to Burnley, but was replaced by Timo Werner after picking up a knock in the warm-up.
"Christian had a scan yesterday that showed a very, very minor injury to his hamstring, very minor. So he's already back outside," Lampard revealed ahead of their second home game in Champions League Group E.
There were concerns Pulisic had suffered a recurrence of the injury that forced him to miss Chelsea's first three Premier League games of the season.
Lampard says Pulisic will continue to be monitored ahead of Saturday's visit of Sheffield United to Bramall Lane.
"It is obviously a relief for the injury to be minor," the Chelsea boss said.
"He made the right decision in not attempting to play the game, because he could have made it worse.
"So it's clearly a relief that he will be back very soon, because he's an important player for us.
"With the actual muscle injuries, it's a hard one to call, it's forever going to be a challenge, some players that play on the edge, have such speed and acceleration in their game, maybe they can be more susceptible.
"I don't think that's a one-fits-all answer, because it's different for everybody.
"From last season we were looking at ways of managing Christian and looking at ways of being proactive in not hopefully getting so many injuries, I know that's something he's experienced previously in his career at Dortmund as well.
"So we're all working in the same direction on that one, to try to get him to be as fit as regularly as possible, because we all know his talent."
Lampard says the physical demands of this unique season, coupled with a lack of a normal pre-season, will have a negative impact on the fitness of all players.
With that in mind, he's also being careful in his use of 36-year old Thiago Silva.
Lampard told his press conference, "Within the squad, you try to have standards and levels to do physical work. We gauge everyday the physical work and input of the players.
"We try to balance it out so everyone is as optimum as they can and every player is different in their own way. Around the general rule of how we train, whether I talk a lot to the sports science team who can give me some clues added to what I see.
"Some of it is with my eye and the staff, then a lot of it is through your relationships and speaking to them. Particularly, when you have an experienced player who is as great of a professional as Thiago Silva is, that conversation is very easy.
"We are managing his training and game time, as we did last week in Russia. I’ll be very up front and honest with him, in terms of what I think, and what he thinks.
"I remember at the back end of my career that I had to change my training programme so I will be open to small tweaks from Thiago."