He transitioned into coaching after quitting his job at Eli Lilly and Company, joining the basketball program at Butler University as a volunteer prior to the 2000–01 season.

[2] Stevens coached the Bulldogs in their second consecutive national championship game on April 4, 2011, where the team again lost, this time to the Connecticut Huskies.

[3] After undertaking a rebuild early in his tenure, Stevens led the Celtics to the NBA playoffs every year from 2014 to 2021, won a division championship in 2016–17, and appeared in the Eastern Conference finals in 2017, 2018, and 2020.

[4][5] He gained a reputation as one of the NBA's best coaches, with his motion offense and stingy defense earning plaudits from fans, peers, and players.

[7] Following that, he won his first NBA championship while with the Celtics as an executive, completing the rebuild that Stevens helped begin and oversee as the head coach.

[12] Besides playing basketball, the young Stevens also enjoyed solving puzzles, a skill he later applied to analyzing opposing teams to find their weaknesses.

[12][20] Before Stevens started training at Applebee's, he was offered a low-paying administrative position as coordinator of basketball operations under then-coach Thad Matta.

[23] Stevens ended up with a school and Horizon league record 30 wins, beating several big-name schools—Michigan, Texas Tech, Florida State, Ohio State—along the way.

[30] Stevens' 56–10 two-year record places him third only to Bill Guthridge (58) and Tommy Lloyd (61) in total wins during one's first two years as head coach.

[50] On Selection Sunday, the Bulldogs were seeded fifth in the West regional of the NCAA tournament and given a first-round match-up with twelfth-seeded UTEP on March 18.

The game was close throughout, but Butler emerged victorious 54–52 when Hayward deflected a Murray State pass into the back court with less than five seconds on the clock.

Perhaps feeling the effects of their 101–96 double-overtime win two days prior, Kansas State got off to a slow start, scoring just 20 points in the first half to trail 27–20.

Stevens correctly anticipated the play call and had Ronald Nored, the team's best defender, switch onto Korie Lucious off a screen.

After a Michigan State time-out, Stevens had his team foul Lucious with two seconds remaining to prevent a potentially game tying three-pointer.

A failed inbounds attempt and a timeout later, Hayward missed a baseline fade-away jumper and Brian Zoubek came down with the rebound for Duke.

[63] Stevens was named as both a Hugh Durham and Jim Phelan Award finalist for the third consecutive year, losing to Mike Young and Jamie Dixon, respectively.

Stevens stated: "I look at this new challenge of not changing and sticking to your core values and making sure you remain humble as a great coaching opportunity.

"[68] Rankings by ESPN's Andy Katz and Fox Sports' Jeff Goodman released shortly after the 2010 championship game both had Butler third for the 2010–11 season.

Bolstered by the emergence of Andrew Smith at center and Matt Howard's success as a perimeter forward, Butler ended up winning a share of the conference title at 13–5.

A week later, Butler beat fellow Cinderella team VCU 70–62 to make it to a second consecutive national championship game.

[74] Financial terms of the contract were not disclosed; however, Butler president Bobby Fong had publicly stated that the university could afford to increase Stevens' base salary to approximately US $1 million a few days prior.

"[83] A few days later, Stevens reiterated that he was very happy at Butler and had no intentions to leave as long as he had the support of the university to continue running the program the "right way.

The Celtics (36–25 overall) finished the month in sole possession of third place in the East behind the Cleveland Cavaliers and Atlantic Division foe the Toronto Raptors.

In the 2017–18 season, the Celtics' roster saw a massive change, as two-time All-Star Isaiah Thomas was traded to the Cleveland Cavaliers in exchange for Kyrie Irving.

[105][106][107] In the playoffs, the Celtics swept the Brooklyn Nets during the first round and then went on to beat the Milwaukee Bucks in seven games during the Eastern Conference Semifinals.

"[57] On the rare occasion Stevens feels the need to correct a player, he does it with "positive reinforcement, just at a little louder decibel", according to former assistant coach Matthew Graves.

[24] "I tell the players 'the Butler Way' isn't easy to define," Stevens says, "but you can see it on the floor when we share the basketball, play with great energy and defend.

"[24][137] The New York Times, USA Today, ESPN, and other commentators attributed Butler's success against teams with superior athletes to Stevens' coaching style.

[55][57][133] The Times remarked, "the Bulldogs are very well prepared for their opponents, and they do not rattle easily", and says that the resulting confidence has led to the team's success.

[58] Asked what his life would be like if he had never taken up coaching, Stevens replied, "If everything else remained the same, I would have been as happy as heck... Friends and family and faith, they're going to take the cake over all this stuff.