Saha suffered an ankle injury during the 2-1 victory over Fulham last month and has since undergone surgery on the problem.
The striker had scored nine goals already in 2011, and his injury now leaves Everton with a shortage of strikers and means a heavy reliance on Jermaine Beckford for the final weeks of the season.
Everton are also suffering from injuries in midfield and defence, with Mikel Arteta and Marouane Fellaini certain to miss Saturday's game at home to Aston Villa on Saturday and Jack Rodwell, Seamus Coleman and Tim Cahill all doubtful.
"We have got a lot of injuries," Moyes said. "Louis has had an operation this week which will probably rule him out for the season.
"It is football, isn't it? You pick up injuries and we try not to talk too much about them but we have a spate of them at this present time.
"Mikel has been away in Spain for a few weeks, recuperating and recovering from his hamstring problem. He is due back over the weekend and we will see how he is."
Moyes believes international friendlies, such as England's game against Ghana on Tuesday, are contributing to clubs' injury problems.
"To have a friendly at this stage of the season is difficult," he said. "I understand why the national teams want them but we are into the last six or seven weeks of the season and you can see the amount of injuries players are having, probably on the back of the World Cup and other international tournaments.
"I think that is why you are probably seeing so many injuries if you look around the Premier League. People are probably not getting to see the best players right now because the football is taking its toll on them.
"They are all involved in so much football and they need a break."
He added: "I do take a lot of pride because I want them to be selected for their country, but I am beginning to doubt if that is what I want.
"I am just beginning to look and say, 'Is it worth it?'. We have lost quite a few players. They don't pay the players' wages - we have to."