England could be without wing Elliot Daly and back row Nathan Hughes for the start of the Six Nations, after both picked up injuries in Wasps' European Champions Cup win against La Rochelle.
Daly, 25, and Hughes, 26, featured in Eddie Jones' Autumn Tests squad.
Outside back Daly injured his ankle against the French side on Sunday, while Hughes damaged knee ligaments.
"When the scans came back it didn't look particularly good," Wasps head coach Dai Young said.
"Elliot has injured his ankle - he has a syndesmosis injury - which is pretty common. He is going to see the specialist to see whether any surgical intervention is required, which depending on the grade of the injury hopefully it won't be.
"Jimmy [Gopperth - Wasps' Kiwi fly-half] and Nathan both have MCL injuries to their knees. Again, we're waiting on the specialist to let us know what is required, but we can safely say even the best picture, which is a grade one tear, will require a minimum of four weeks.
England begin the Six Nations against Italy on 4 February, and finish their five games in the tournament on 17 March at home to Ireland.
Daly has scored six tries in 19 England Tests since making his debut against Ireland in the 2016 Six Nations, and was part of the British & Irish Lions 2017 touring party.
Hughes missed the last Autumn Test against Samoa through injury with a different knee problem and has 12 Test caps.