Since Brad Stevens started his NBA coaching career with the Boston Celtics in 2013, he has been labeled as one of the best young coaches in league.

His ability to take average players and make them great is one thing that has at times separated him from other coaches in the league. Though, at least one Celtics great isn’t sold on him.

Butler days: When Stevens took over as coach at Butler, he was the youngest coach in the NCAA at age 30. He led them to the National Championship in 2010 and 2011, where they lost both games. But it showed how good of a coach Stevens was at a non-Power 5 school.

There were two notable guys that Stevens coached that excelled into the next level:

Gordon Hayward: Hayward was a 6-foot-7 forward from Brownsburg, Indiana who was not rated by ESPN. He came onto the scene in the 2010 NCAA tournament, where he averaged 16 points per game in the tournament. That led to him being chosen ninth overall by the Utah Jazz, where he went on to become an All-Star.

Shelvin Mack: Another guy who was not high recruit coming out of college, Mack proved that he could play in the NBA after leading the Bulldogs to the 2011 national championship. Mack was drafted 34th overall where he has become a decent backup point guard for many NBA teams over the course of his career.