Announcing his retirement in the lead-up to the Magners League play-offs, O'Kelly will no doubt give his all as Leinster step up their pursuit of a third piece of silverware in as many seasons.
The big lock's commitment to his club, province and country over the years cannot be questioned, as departing Leinster coach Michael Cheika explained.
"I think everyone knows what Mal has contributed as a player. He has been a pro for a long time and the mere fact that his standing within our squad at the moment, where he's well in line to start the match this weekend, pretty much says it all about him," said Cheika.
"On a personal level, from the first day I came in, he was open to change. He helped me in making the change in a different way; he may not be the captain's style of player but he undertakes his influence in the team in a totally different way, more as a colleague in the changing room.
"He's always open to become better as a player. Even now we have come off the training field and he was out there running around and still wanting to improve and be better.
"He has been an unbelievable influence on the team and on me and he has been an integral part of the change that I hope has happened in Leinster Rugby over the last five years."
The 35-year-old has maintained a high level of fitness throughout Cheika's tenure and he, most notably, played every minute of the quarter-final, semi-final and final of Leinster's memorable Heineken Cup-winning campaign last year.
He became Ireland's most-capped player in 2005, breaking Mike Gibson's long-standing record of 69 caps, and his 92nd and final appearance in green came as a replacement against Italy in last year's Grand Slam-winning run.
Praising the Templeogue man's durability, Cheika added: "One of the big things that I've noticed with him is that over the first season I was here he had some longer term injuries and he worked hard to get himself into a situation where he could play week in, week out.
"We didn't have a lot of resources back then in terms of depth in the squad, but he was able to overcome groin and knee problems and he worked hard.
"He's sometimes at the butt of some team jokes in terms of tardiness and attention to detail regarding the calendar, per se, to put it elegantly! But he does all of his homework, which isn't easy when you're talking about (games) week in, week out in your mid 30s.
"He's still in great nick. He still has a great engine in terms of where his running is concerned and he's still eager to be involved in the development of the lineout and his tighthead locking of the scrum. These are things the team is going to miss."
Cheika recalled a special memory of O'Kelly that stands out for him, from March 2008 when he broke the Leinster caps record at Stradey Park.
"A few of the young bucks have come and tried to knock him off his perch and they haven't been able to as of yet. In the last four years he has been extremely durable and when required does his job," explained the Australian.
"I have a real picture in my mind about the way he played on the occasion of his then record breaking 140th cap away to Llanelli.
"He had just missed out on selection for the international team and we had to win to stay in the hunt. That was the year when we won the Magners League, it was pouring rain and he worked like a dog all game.
"He got a try, just burrowing his way over to win us the game, and that says it all about the guy. He just wants Leinster to do well and he'll be a big loss for the club."