Heading into his junior season, the Ohio State guard was playing in an open gym when the team's associate strength and conditioning coach saw a member of the team's present suddenly matched up with one of the more notable names of the past.
"I watched a pickup game one day during the summer when he got switched off and was guarding Scoonie Penn," Richardson said. "As quick as Scoonie Penn is, he stayed in front of him. He's come a long way, I will say that."
As Richardson put it, Diebler has made significant gains in more than just his shooting touch. His shooting struggles as a freshman were well-publicized, but Diebler found himself far behind his teammates from a flexibility standpoint upon his arrival in Columbus.
Asked where Diebler ranked among all the players he has worked with in his 20-plus years as a strength coach, Richardson said Diebler was "one of the worst.
"A lot of athletes that we see come into college from high school have a lot of problems with what we call their hip mobility, their ability to stay in a stance, stay in a squat. It's not just muscular flexibility. It's about the joint mobility. We had to do some work with him."
It was enough that Diebler has had to continually engage in extra stretching and workouts with both Richardson and athletic trainer Vince O'Brien.
"I always knew I wasn't flexible but I didn't know it played such an important role in basketball," he said. "Think about it: Your hips are so bad you can only stay in a defensive stance for so long."
To improve in that category, Diebler has engaged in extra stretching and has undergone frequent foam rolls – a foam pad that helps stretch the muscles in his hips.
"It's like anything else: some people are naturally more fluid than others and some people are naturally more muscularly tight," Richardson said. "Some people are really flexible without training. Everybody is a little bit different but you have to find out what their weak spots are and get them better at it."
In Diebler's case, the weak spot was his flexibility. That in turn affected his ability to guard Division I basketball players.
During the 2007-08 season, OSU head coach Thad Matta abandoned his patented man-to-man defense for a much-despised zone for the first time in his coaching career. Looking back, Diebler said he was the weak point at that end of the court.
"That's probably why we were playing zone," he said. "My defense was pretty bad. I'm not the most flexible person, so for me to stay in a stance for a long period of time was a struggle."
Throughout that season, Diebler struggled to connect from the three-point range as well. After entering OSU as the state's all-time leading prep scorer from Upper Sandusky, he shot 28.9 percent (48 for 166) from behind the arc and lost his starting spot eight games into the season.
He has since admitted to feeling plenty of stress that season, but Richardson said it never came across at the time.
"I'm sure it probably was on his mind," he said. "Now he'll tell you that it was, but he never really showed it. I think he just tried to find other ways to help the team win."
The Big Ten tournament showed proof of his progress. With the score tied at 66 in the final seconds March 12 against Michigan, it was Diebler who was matched up with U-M guard Manny Harris. One day later in a victory against Illinois, it was Diebler who was charged with sticking with point guard Demetri McCamey as he attempted to come up with the game-winning shot in regulation.
Harris connected on his shot after rubbing off a screen, while McCamey was not able to get a shot off before the buzzer.
To get to that point, Richardson said Diebler had to be able to physically get his body in position to play defense. Matta said that it was a weakness in Diebler's game out of high school but added that he had other strengths that helped offset his lack of flexibility.
"He couldn't move laterally," the coach said. "To his credit he's done a great job of working at it. Before every practice he goes over and does the exercises that we've given him. It's been amazing watching his lateral quickness – his hip flexors as they call them – get better."