Everton defender Phil Jagielka has undergone a second knee operation and may not play again until after Christmas.
Jagielka, 27, has been sidelined since damaging knee ligaments in April but had been hoping to return to action before the end of November.
However, a problem, described by Everton as “a small cartilage tear”, means the England international’s comeback will be delayed.
The former Sheffield United player had an operation on Wednesday, Everton revealed.
Moyes said: “Jagielka had an operation on a tear in his meniscus, which is the cartilage in his knee.
“We think [it has set him back] four to six weeks. He was down initially but he’s on the road to recovery now.”
Moyes told the official club website that striker Victor Anichebe has also suffered a complication in his recovery from a knee injury.
Anichebe has not played since February and the 21-year-old appears some way off a return to the first team.
Moyes said: “Victor’s not in a good way either. He had the pin taken out four to six weeks ago which had been catching on the side of his knee.
“Now what has happened (is that) he has a massive growth of bone and has a really big knee at the moment. We don’t know how long it will be.”
The double blow simply adds to Everton’s recent woes.
They have not won in their last seven games and also saw Mikel Arteta suffer a setback in his recovery from knee ligament damage earlier this week.
The Spanish midfielder suffered the injury in the same game as Anichebe – away to Newcastle back in February.