The pair were teammates for a year and a half at Hillsborough, where Buxton remained until 2015 while Clarke embarked upon a tour of clubs in England's Football League.
The former went on to play for Rotherham United and Bolton Wanderers before retiring last year, in which time the latter has morphed into one of the Championship's most dangerous goalscorers.
Sheffield Wednesday make the 3.7-mile trip to Sheffield United's Bramall Lane ground later this evening, and discussing the game on Alan Biggs' TV show on Thursday, Buxton said of Clarke: "I just remember playing one-on-one against him in training and he had such ability, he would just breeze past me a couple of times if he fancied it.
"He’s one of those players that in my personal view, he could play higher up than the Championship regularly, certainly in the bottom tier of the Premier League, I felt like, and who knows what could happen from there.
"But again it’s down to does a player want that? Some players will say I don’t need that, they can’t see the wood for the trees while they’re stuck in that. It has to be somebody that wants to get the most from their career."
Clarke has scored 20 goals in 53 Championship games for Sheffield United, having struck 35 in his previous 207 at that level.
And Buxton, who set up Sheffield Wednesday's last derby winner in February 2012, added: "I knew he could do that because I’ve seen the quality he’s got, both feet. He’s strong, he’s got decent pace, he can finish. So to me it’s no surprise that happened.
"There’s that management side of it (Chris Wilder's influence), the relationship between players, you can bring the best out of them."
Wilder is likely to choose between Clarke, who has scored or assisted twice in his last three starts for Sheffield United, and another ex-Sheffield Wednesday striker, David McGoldrick, as to who partners Billy Sharp against the Owls.