DETROIT-- Purdue forward Mason Gillis came off the bench during the first five games of his redshirt freshman season in 2020-21 as the Boilermakers got off to an uneven 3-2 start. Then, while in search of the right lineup combination, coach Matt Painter swapped Gillis into the starting lineup on Dec. 12, relegating a veteran to come off the bench instead.

"I got the spot, and I took somebody's spot," Gillis recalled. "I saw him not necessarily get upset about it — and he's a great guy who I love to this day and we have a great relationship — but he almost came off defeated instead of still trying to fight for his spot back."

For three years, Gillis remained either a full-time or part-time starter for Purdue. Then, entering his fifth season with the program, he was faced with the same situation as the veteran who'd come before him.

Painter explained to Gillis that he was leaning toward going with sophomore forward Trey Kaufman-Renn in the starting lineup over Gillis entering the 2023-24 season. The news left Gillis, who had started 63 career games, looking back to three years earlier, when he was on the other side of this situation. 

"I didn't want that to be myself," Gillis said. "Whether I got my spot taken or not, I wanted to provide for the team and play to the best of my ability, just because that's who I am. No matter what anybody else does, I can control what I'm doing. Having that experience and then going through this experience, I'm happy with how I handled it." 

So is Purdue. With Gillis embracing his role as the sixth man, the No. 1 seed Boilermakers are on the cusp of their first Final Four appearance since 1980. They will play No. 2 seed Tennessee on Sunday in the Midwest Region final as the only team to make the NCAA Tournament's second weekend with the same starting lineup for every game during the season.

Barring an unexpected shakeup, the Purdue unit of Braden Smith, Lance Jones, Fletcher Loyer, Kaufman-Renn and Zach Edey will be the first since 1978 to start every game in a season for the Boilermakers.

"I think it's a comfort thing," Kaufman-Renn said. "It's worked. It's one of those things where, when you're in practice, you do what you practice. That starting five is out there together a lot in practice, and we're able to put it on the floor together."

Gillis earned his degree in just three and a half years and would have been free to leave as a graduate transfer once he caught wind of the fact that he was unlikely to start this season. He chose a different path, and it's paid dividends.

At 6-foot-6 and with an outside shooting stroke, he provides a change of pace at the power forward slot. In an 80-68 Sweet 16 victory over No. 5 seed Gonzaga on Friday, Gillis quietly checked in for Kaufman-Renn after the game's first media timeout. Within minutes, he hit a pair of big 3-pointers to help the Boilermakers withstand an early offensive barrage from the Zags.

"Mason Gillis is really a starter, but I like bringing him off the bench," Painter told CBS Sports. "I think he's a weapon where he comes in and changes the game in terms of style of play. Trey is more of a post-up type player who can play in the high post or the low post."

To begin the second half, Kaufman-Renn's physicality helped the Boilermakers begin to pull away. With Gonzaga big man Ben Gregg beginning the second half on the bench with three fouls, the Bulldogs went small and were ill-equipped to simultaneously deal with both the 7-foot-4 Edey and the 6-foot-9 Kaufman-Renn, who scored Purdue's first six points of the half.

"We're not perfect, but I think we've tried to make some adjustments," Painter said. "The great thing about it is we can play a lot of different ways. I think that's the important piece of it, where is if something is not quite working, we can make some adjustments even though we haven't adjusted our starting lineup."

Gillis is now just two classes away from completing his MBA in management. Though he hasn't started a single game, his playing time is actually up just a tick from last season.

"I was given two options," Gillis said. "Either grow with it or let it beat me up."

Because he chose option No. 1, the Boilermakers have remained a model of consistency throughout the 2023-24 season.

"When you have a great team," Painter said, "you have more starters than five people."