Northampton fly-half Fin Smith is suffering with a calf strain that may put him out of England’s Six Nations opener against Wales on 7 February.
The 23-year-old withdrew from the Saints line-up to face Bordeaux-Begles on Sunday and is awaiting the results of a scan on the injury.
“We’re still waiting to see how long that is from a scan point of view,” said Northampton director of rugby Phil Dowson.
“It’s probably minimum two weeks, but with a muscle injury it’s hard to give a timeline beyond that.
“It’s not months and months and he’s not going to be back this weekend, so somewhere in between that.”
England take on Wales in three and a half weeks, with their Six Nations squad set to be named next week.
After the opening round of action, England travel to Scotland on 14 February and then take on Ireland at Twickenham on 21 February before the Six Nations’ rest week.
Smith came off the bench in the opening-round defeat by Ireland in last year’s competition and was promoted to the starting XV for the remaining four matches of England’s campaign.
Steve Borthwick’s side finished second in a hugely encouraging campaign, and Smith won selection for the British and Irish Lions tour of Australia over the summer.
However, while Smith endured a disappointing time with the Lions, unable to exert pressure on Finn Russell for a Test spot, George Ford impressed in England’s Tests against Argentina and the United States.
Ford was preferred during the autumn, starting at 10 in victories over Australia, New Zealand and Argentina, while Smith, unable to offer Marcus Smith’s versatility, was restricted to a win over Fiji and the fringes of the matchday 23.
“It is hard to take,” Smith told BBC Radio Northampton’s Saints Show in December.
“I have absolutely loved how good it feels to wear the England 10 shirt; having that taken away from you does hurt.”
Frenchman Anthony Belleau, signed from Clermont Auvergne in the summer, filled in for Smith in the defeat by Bordeaux-Begles and has adapted quickly to life with Saints.