The year before Butler University embarked on the first of two Cinderella runs to the NCAA title game, Stevens and his Bulldogs were unceremoniously bounced from the opening round of the tournament when Thornton, an NBA-bound sophomore, poured in 30 points to help eighth-seeded LSU edge ninth-seeded Butler.
That game invariably came up in conversation when the two talked for the first time last week after the Celtics acquired Thornton as part of a three-team trade with the Brooklyn Nets and Cleveland Cavaliers.
"I told him I wouldn't hold it against him," said Stevens, before joking that Thornton should instead, "bring it up to [player development coach] Ron Nored," who was a starter in the Butler backcourt for that game.
The 27-year-old Thornton arrives in Boston in the final year of a contract that will pay him $8.6 million. While absorbing that salary was the cost of doing business in a deal that also netted Boston young center Tyler Zeller and Cleveland's 2016 first-round pick, both Stevens and president of basketball operations Danny Ainge offered high praise for Thornton and how he can help the team next season.
"Marcus can bring us some scoring, probably a bench scorer, and can really get hot in stretches -- he had a 42-point game [against Indiana] last year," noted Ainge. "He's a guy that can shoot the ball from the 3-point line and adds shooting and depth to our team."
For his career, Thornton has averaged 13.4 points and 26.1 minutes per game while shooting 43.1 percent from the field and 36.1 percent beyond the arc. Acquired by the Nets at last year's trade deadline to provide the sort of bench scoring that Jason Terry couldn't, Thornton averaged 12.3 points, 23.8 minutes and what would be a career-best 38 percent beyond the arc over the final 26 games of the regular season.
For a Celtics team desperate for a scoring jolt, Thornton has the potential to make an impact.
"Marcus can score," said Stevens. "I think any time you think about your team and you think about what your needs are, putting the ball in the basket helps a lot and I think Marcus will complement the guys that we have back there, but he can also run off screens both directions, shoot the basketball. He can get it off pick-and-rolls or handoffs and shoot the basketball. And he can create his own shot going at full speed, which is hard to do.
"I'm really familiar with Marcus. Marcus knocked us out of the tournament in 2009, basically single-handedly. He's had a really solid career but with some really unbelievable moments already."
It's probably safe to assume that Thornton is not long for Boston, though he could certainly state a case to stick around with his play. More likely would be Thornton's emerging as a potential in-season trade asset if he can showcase his abilities early in the year.
Stop me if you've heard this one before: The Celtics have a growing logjam at the shooting guard position. Boston has already agreed to a four-year, $32 million contract extension with starter Avery Bradley and used first-round picks on combo guard Marcus Smart and swingman James Young in last month's draft.
Boston must balance a desire to develop young players with giving Thornton a chance to prove himself. It's on Stevens to find the proper balance, but if last season is any indication, Thornton will get every opportunity to showcase his talents (see: Jordan Crawford, Courtney Lee).
The Celtics, seemingly on track for another rebuilding season, were able to stomach Thornton's salary and brought back additional assets while giving up only a conditional second-round pick (and absorbing the salary with a $10.3 million trade exception generated in another swap with the Nets last summer).
There's virtually no downside for Boston, other than forcing Stevens to continue figuring out how to keep all his players happy.
The last time Thornton was traded in a contract year, he parlayed an increased opportunity in Sacramento into a four-year, $31.2 million extension. His next contract is likely to be determined in part by what he can do in Boston.
The Celtics should be acquiring a motivated player who -- one way or another -- can help the team's future.