Fabianski has made only six appearances for the Gunners this season following Szczesny being named first choice at the Emirates Stadium.
Despite a lack of games for his understudy, Szczesny believes that he has to keep on his toes knowing that such a good shotstopper his waiting in the wings.
"I think the quality of goalkeepers at the club is as good as anywhere in the country," Szczesny told the club's official website.
"I believe Lukasz is the best number two in the country. Every time he goes in goal the team is confident he will do a good job, and to have someone like that behind you gives you a lot of motivation to work hard at the training ground.
"I know I have to be at my very best in every game because he is waiting to take my spot. It helps keep you sharp and to be at your very best."
Arsenal, who are currently third in the Premier League table, host Chelsea on Saturday.