The South African-born hooker may return this weekend but Cronin, who has battled for the shirt with Aaron Dundon during that time, has impressed in his absence.
The 27-year-old will make his 12th appearance of the season this weekend - his sixth in as many European Cup games - and O'Connor, who joined Leinster from Leicester Tigers this summer, is not surprised by Cronin's form.
"I'd seen Seán play a lot - we flirted with signing him when I was at Leicester," O'Connor told the Irish Times.
"One of the things that I spoke to him about was the hard things in the game and the things that don't come overly natural to him.
"I think he's been exceptional in those things and he's worked incredibly hard in the environment to improve those things because he's incredibly talented.
"Seán does things on the field that very few hookers can do and full credit to him for how he's knuckled down to work on those things in his game."
Cronin made his first RaboDirect PRO12 start since October in Leinster's win against Connacht earlier this month and he is determined to retain the shirt in the league.
The 27-year-old is aware that Strauss' return - well ahead of schedule - will add extra pressure in the coming weeks, but he is firmly focussed on his own game.
"It has been great to get the run of games," he said. "I don't think there is anything better. A player will always tell you that.
"Matt has shown a bit of faith in me, by giving me a few starts. It has been good to get a run of games and the fact that we are still in the hunt for the quarter-final of the Heineken Cup and going well in the Rabo. It has been great to be a part of."
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