The Poland international has become a mainstay of Arsenal's starting XI this term after spending time out of the side at the back end of last season.
Szczesny made his 100th Premier League appearance in Saturday's 2-0 victory over Fulham, and marked the occasion by keeping his 10th clean sheet of the campaign.
"Certainly a part of his improvement is mental because he's more mature," the manager told the club's official website.
"His decision-making is cleaner, sharper, quicker. He was always a very talented boy but because he's intelligent he learns quickly from experience.
"I'm happy that I always gave him the confidence because he's developing very well into a very strong goalkeeper and today certainly nobody would question that he's one of the top five goalkeepers in the Premier League."
He added: "That defensive solidity of course is the basic work you have to do to be efficient at home.
"Maybe what is even more important is to have that solidarity at home because it gives you time to fatigue your opponent, time to stretch them, time to dominate them and get the game completely in their own half.
"The longer that lasts the more you have chances to score."
