Alun Wyn Jones is the greatest Welsh second row of all time, according to Martyn Williams.
Jones makes his 200th appearance for Pro12 leaders Ospreys against Leinster in Dublin on Friday evening.
The 31-year-old has played 102 times for Wales, and Williams, who has 100 Wales caps, says Jones is a phenomenon.
"I'm not surprised he's done what he's done. When you saw him as a kid you knew he would be something special," said the former Lions flanker.
"I think he's Wales greatest second row there's ever been - there have been some greats you can argue about - but he's just a phenomenal player."
Jones makes his first start of the season against Leinster after scoring a try after coming on as a substitute against Treviso last week.
Ospreys go into the match on top of the Pro12 after bonus point wins in their opening three games.
Jones played for Swansea before joining Ospreys in 2005 and has played six Tests for the British and Irish Lions, captaining them in the decisive 41-16 third Test win against Australia in 2013.
Former Ospreys team-mate Shane Williams says Jones is a model professional, an inspiration and a "nightmare" to train against.
"His drive and his desire is never questioned and when Alun Wyn Jones is training well and playing well it's infectious - players around him want to do the same," said Williams, Wales' record try scorer.
"He would go flat out, whether it was touch rugby, contact, set-plays or whatever.
"He probably caused more injuries to me in training than the opposition did in matches. He was an absolute nightmare, I've got to give him that."
Jones has resisted bids from clubs around to world to stay in Wales, signing an extension to his national dual contract with the Welsh Rugby Union and Ospreys in January 2016.
"He is certainly a good enough player and of high enough quality to have gone elsewhere - overseas or wherever," added Williams.
"He wants to achieve greatness with the Ospreys and it would take someone brave not to pick him for the weekend really. It's part of the reason he's got this milestone.
"He's very fit anyway, he hasn't had major injuries and he's still got that desire, he's still got that will to do it.
"He certainly hasn't slowed down on the rugby field and I'm sure he's got plenty left in the tank."