Benitez has warned his players not to take victory over Rubin Kazan, who are unbeaten in the Europa League, for granted.
He said: "Some people are saying they are not very famous but they knocked out Atletico Madrid and Levante and they were doing very well.
"It's a tough game to play. People think we will score four goals but I think that will be very difficult. They are very compact, organised, solid and good on the counter-attack.
"They have [Jose] Rondon, who used to play for Malaga, and he is very strong and quick. There is also [Roman] Eremenko and he is a very good player between the lines.
"Maybe it will be difficult here [at Stamford Bridge] and hopefully in the second game we can do well."