England and Bath back Anthony Watson will be out of action for at least four weeks after sustaining a knee injury in his side's Champions Cup defeat to Harlequins on Saturday.
Watson underwent an MRI scan on Monday, which revealed the 25-year-old will not require surgery, but he is not expected to return before Christmas.
Stuart Hooper, Bath's director of rugby, told BBC Radio Bristol: "Anthony is in a brace, but doesn't require surgery and we will get him back ready to perform as soon as possible.
"It's a short term thing that Anthony is working on and we need to get right. He is absolutely one of the most diligent professionals around.
"Anything to do with himself or getting ready to play on the field. Alongside our performance department, we will be working on it 24/7 to get him back as soon as possible."
Meanwhile, club captain Charlie Ewels limped off against Harlequins, with his injury since being confirmed as a medial ligament tear.
"Charlie has a similar mechanism of injury," Hooper said. "It's a knee injury. He's going to see the surgeon tomorrow to see what the best steps are next."
"Both [Ewels and Watson's issues] are collision injuries, which happen. There's nothing we can do."
Watson played in all six of England's games at the Rugby World Cup in Japan between September and November, including Eddie Jones' side's defeat to South Africa in the final.