Liverpool lose Benayoun and Riera
"We will have to wait and see how they progress but hopefully in three weeks they could be available," manager Rafa Benitez told the club's website.
"We are disappointed because there are too many things at the moment we can't change. Both players are wingers as well and for them to be out at the same time is bad news for us."
Liverpool are seventh in the Premier League, 11 points behind leaders Chelsea, and also in danger of making an early exit from the Champions League.
There was better news on other injured players, with Benitez hoping the international break would allow his depleted squad time to recover for the next game against Manchester City on November 21.
"Sometimes a break comes at a bad time because you don't like to see your players flying all over the world but this time it gives us a chance to get some players back," said the Spaniard.
Benitez said defender Daniel Agger, who suffered a knock in the 2-2 draw against Birmingham City on Monday and withdrew from Denmark's friendlies against South Korea and United States, could be back in training in a few days.
The condition of right back Glen Johnson, who pulled out of England's squad for Saturday's friendly against Brazil, was also encouraging.
"Hopefully it's not too serious and he could be available again in a week," said Benitez.
Spain striker Fernando Torres will need two or three weeks treatment on his groin strain.
"I was talking with him this morning and he is doing well," said Benitez. "Hopefully he can be running in a few days and we will see how he progresses."