Arsenal boast the second meanest defence this season, conceding 13 goals, and Cech's clean sheet against Villa, which came in his 349th Premier League game, was his seventh of the campaign.
"He's changed us completely in that back four. He's a talker, he believes in us all," Walcott told the club's website (www.arsenal.com).
"That's why he wanted to join us and having that presence behind you is always nice. He's very commanding, he's a leader in the dressing room as well.
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"From when we signed him, we all knew how good he was (after) what he achieved at Chelsea," added Walcott.
Cech won the Premier League title four times at Stamford Bridge and was also instrumental in their 2012 Champions League final victory over Bayern Munich.
Arsenal's next Premier League game is against second-placed Manchester City on Dec. 21.
(Reporting by Simon Jennings in Bengaluru; Editing by Tony Jimenez)
