Benitez told Sky Sports News: "If you have a lot of players playing a lot of games then they are more at risk than the others.
"You want to keep your key players. Torres was playing well, he was scoring goals, he is really important to us. To lose a player like him for three or four games is a big problem for us.
"He has had three hamstring injuries with the Spanish national team so it is something that we need to analyse.
"With us it is OK. He has had one (injury) in one year and a half. With the Spanish team, three times, so we need to check why.
"You know my ideas about the internationals, so I am really disappointed.
"For me he is playing too many games. It would be easier to keep him here. It's the same with the other players."