Everton defenders Joseph Yobo and Tony Hibbert could miss the opening weeks of the Premier League season.
Centre-back Yobo has been hampered by an ankle injury during Nigeria's World Cup qualifiers recently, while full-back Hibbert may require surgery on the knee problem he sustained at the end of last season.
The loss of the duo would be a setback for David Moyes as he prepares his side for their first match of the new season against Blackburn on 16th August.
Yobo said: "I have had an ankle injury for a while.
"I was supposed to rest it but we had crucial games to play and were short at the back so I just had to force myself to play."
Yobo is now on an extended break and Moyes must hope the rest allows the player's injury to recover naturally.
Hibbert is crossing his fingers an operation will not be required on an injury sustained at Arsenal last year which turned out to be far worse than he initially feared.
"When I did it, I felt okay," he told the Liverpool Daily Post.
"We didn't realise at first how bad it was. I have had tweaks in my knees before and it didn't feel anywhere near as bad.
"But the scan was 10 times worse. I ruptured my medial ligaments. They have basically come completely off the bone at the top where the nerve endings are, which is why I wasn't getting much pain."