"He is a coach that likes to push his players and get the most out of them," Gardiner told the Toronto Star on Wednesday. "I think that was what he was doing with me.
"I have a lot more potential than what I've been doing. I think [his approach was] good for me. It will help me down the road."
Gardiner's contract, announced Tuesday, reportedly is worth $20.25 million (an average annual value of $4.05 million). He was a restricted free agent.
"I am happy to be a Leaf for a really long time," Gardiner told reporter Kevin McGran. "That was a big part of it ... commitment. I thought having five years and the money was awesome. The security for me was good. It just shows the Leafs have a lot of faith in me."
That belief wavered at times last season, when Gardiner was scratched twice by Carlyle and saw his ice time vary wildly. He scored 11 points (two goals, nine assists) in the final 14 games to finish with 31 (10 goals) in 80 games, second among Maple Leafs defenseman behind Cody Franson's 33 points.
Gardiner's average ice time of 21:04 was second behind Dion Phaneuf (23:34), ranging from a low of 13:59 to a high of 26:21.
"[ Randy] thinks a lot of Jake," Maple Leafs general manager Dave Nonis told the Star on Tuesday. "He does push him in certain ways that Jake had to adjust to, but it's only because Randy knows how good Jake can be. Having Jake locked up for five years will make Randy very happy."
Gardiner has 17 goals, 65 points and a minus-5 rating in 167 NHL games over three seasons.
"He had a great year last year," Nonis said. "He's clearly still improving. This isn't a player who has reached his ceiling yet. There's a lot more for Jake to give. He's already a very good player. ... We think there's a chance he could improve dramatically over the five-year period."