Arsenal manager Arsene Wenger feels added maturity has put Wojciech Szczesny among the top five goalkeepers in the Premier League.
The Poland international, 23, 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," Wenger 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."
Arsenal top the Premier League after 22 matches, one point ahead of second-placed Manchester City.
The Gunners have shipped just 19 goals in the league, with six of those coming in a 6-3 defeat at Manchester City in December, and Wenger believes a stern defence aids the club's progression.
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."