Steve Borthwick is not ruling Owen Farrell out of the British and Irish Lions' first Test against New Zealand next week.
Farrell will not face the Maori All Blacks on Saturday after he was declared unfit due to a quadriceps injury the England man is said to have sustained in training.
Lions assistant coach Borthwick on Friday said that Farrell may recover in time to take on the world champions at Eden Park next Saturday.
"He didn't train today, he's had a grade one muscle strain," Borthwick said.
"The medical team will take great care of him. Hopefully he'll be back on the field as soon as possible.
"When exactly it happened, I can't tell you. It was felt yesterday, dealt with immediately, and he went into recovery protocols straight away."
Asked if 10 days was a realistic timeframe for Farrell to return, Borthwick said: "I certainly don't go by that.
"I listen to our medical team, who are far more qualified than I am. He'll be back as quickly as he's fit and able."
Borthwick added: "You deal with the hypothetical and I'll deal with what the facts are. He'll be back as soon as he's fit and able to be back.
"Owen is an incredible professional. We've got a fantastic medical team and he'll be back on the field as soon as he's physically able.
"They'll monitor that on a daily basis, and we'll get updates on a daily basis. If you want any more detail on that you'll have to ask Warren [Gatland, Lions head coach] when he's next up."