Before he was a basketball player, Mason Gillis was a baseball player. Good enough to compete in the Little League World Series. Good enough that choosing basketball over baseball was a genuine sacrifice, not a formality. He grew up in New Castle, Indiana — a town of 18,000 people in Henry County, about fifty miles east of Indianapolis, where the high school gym is called the Fieldhouse and holds 9,325 seats because this is Indiana and basketball is religion.
Gillis was born on November 24, 2000. His parents are Tammy McCall and Bill Gillis. His older sister Lauryn played volleyball at USC before transferring to Wisconsin. The family was built for competition. At New Castle High School, Gillis was a four-star recruit who averaged 21.6 points, 12.2 rebounds, and 2.3 assists per game as a junior, shooting 59.5% from the field and over 45% from three while leading the Trojans to a Class 3A Regional title. He was one of the best two-sport athletes in the state — and then he chose one sport.
In June 2018, Gillis committed to Purdue. The Boilermakers were building something under Matt Painter, and Gillis wanted to be part of it. But a knee injury during his senior year of high school forced him to redshirt his freshman season at Purdue, sitting out the entire 2019-20 campaign. He watched. He rehabbed. And when he finally got on the court, he didn't leave for four years.
At Purdue, Gillis appeared in 132 career games with 63 starts, averaging more than 20 minutes per contest every season. He amassed 827 points, 548 rebounds, and 179 assists. He shot 40.7% from three-point range across four seasons — seventh on Purdue's all-time list. On February 1, 2023, he broke the Mackey Arena record with nine three-pointers in a game against Penn State. He was named Big Ten Sixth Man of the Year in 2023-24 after averaging 6.5 points and shooting 46.8% from deep — sixth nationally among players with at least 50 made threes. He earned his bachelor's degree in three and a half years. He was a three-time Big Ten All-Academic Team honoree.
And then there was the run. In four years, Purdue earned a top-four seed in the NCAA Tournament every time Gillis played. He appeared in 11 Tournament games, starting five. In 2024, the Boilermakers reached the national championship game behind Zach Edey — where they lost to UConn. Gillis had tasted everything college basketball had to offer except the last bite.