Alex Mitchell has emerged as a doubt for the Nations Championship in July after sustaining a pulled hamstring during England’s training camp last week.
Northampton director of rugby Phil Dowson revealed that Mitchell is set to miss the rest of the club season, even if the Gallagher Prem leaders reach the Twickenham final on June 20.
The Prem showpiece takes place two weeks before England face back-to-back world champions South Africa in Johannesburg, with fixtures against Fiji in Liverpool and Argentina in Buenos Aires completing the summer tour.
England head coach Steve Borthwick now faces the possibility of being without his British and Irish Lions scrum-half for all or some of the Tests.
"He's pulled it and he's done a decent job on it," Dowson said. "It's going to be a push to get him any rugby for us for the rest of the season.
"It's frustrating and every director of rugby would say that. Steve [Borthwick] would say that when people get injured on club time and they're about to go and play in internationals. It's the nature of the beast. These things happen."
Mitchell, the only Lions player to be named in every matchday squad in Australia last summer, was forced to sit out the final two rounds of the Six Nations after pulling the other hamstring.
Dowson plans to hold talks with Borthwick and England's head of performance Phil Morrow in response to Mitchell's injury, although he added that "we've got to make sure we don't go looking for shadows".
"How do we mitigate the risks?" Dowson said. "What does the training look like? Did he get the training he wanted? What do the metrics look like?
"I don't think it was a ludicrous session in terms of volume. You've got to be careful of saying 'this session was hard or this session wasn't'. It's unfortunate.
"Maybe there are things we can do better, but I'm not going to start casting aspersions until I've spoken to Phil Morrow and the rest of the medical team to find out what their thoughts are as well.
"We'll talk directly to the medics and Morrow and Steve and work out if anything can be done slightly differently in the future."
