Throughout his career, Xavier Tillman Sr. has always taken the initiative when he was needed. Despite his reliability, it is not an easy role to fill.

“Yeah, I would say it was difficult at first because ego and pride get in the way,” he told the author a day after helping the Celtics take a 3-0 lead in the NBA Finals.

“You dream that you’re going to do something big and you want to be the star of the show and stuff. But when you realize that you have to be a star in your own role, I think it makes it easier to do as much as you can day in and day out, whether it’s in the weight room or on the field in your own individual workouts. When you’re not playing, you encourage your teammates. You just have to embrace your role and do everything you’re supposed to do in it.”

Tillman worked carefully with Celtics assistant coach DJ MacLeay to make sure the former Michigan State star would be ready if Joe Mazzulla called him up – which went from possible to probable after Kristaps Porzingis suffered a torn retinaculum and a dislocated posterior tibial tendon in Game 2 against the Mavericks.

“I was super, super ready for it,” Tillman said during an appearance on Spaces on the NBA account on X, formerly Twitter, with host Jason Fisher. “I felt like my coach, I’ll call him D. Mac, was working out with me the whole time… He was kind of preaching the confidence that comes from staying ready, like, ‘Do the work.'” … He really gave me exactly the blueprint that I needed to know before I went.

“When I got the opportunity to play, I wasn’t as nervous anymore. At that moment I thought to myself, ‘You’ve come this far, we’re here now, this is the championship, you might as well go out and leave it at that.'”

He responded by making a key contribution to Boston’s title run. In Game 3 in Dallas, the 6’0″ and 240-pound player showed his versatility on defense, especially when he adjusted to Luka Doncic and blocked his shot twice.

Tillman also grabbed four rebounds and hit a three-pointer from the corner in the third quarter, arguably the Celtics’ best quarter of the postseason.

“I don’t know if I’ve played a game in a long time where I wanted to win so much,” Tillman, who the Celtics signed at the trade deadline from an injury-plagued Grizzlies team, said on Spaces. “I was so mentally prepared.”

Jaylen Brown, who saw the work Tillman was doing behind the scenes, also realized that Porzingis’ injury likely meant Boston would rely on the fourth-year veteran while letting Al Horford set the pace.

“JB had been watching me practice for the last few weeks and he came up to me and said, ‘I think you’re going to get a chance to play, so be ready.’ And I said, ‘I get it.'”

It’s fitting that Brown was the one who passed the ball to Tillman for that three-pointer from the corner in front of the Dallas bench.

“I think Lively, Dereck Lively (II), was right behind me when I shot. He was like, ‘No way,’ and when I hit, I looked right at him, smiled and said, ‘Yup,'” Tillman said in his interview at Spaces.

“For me, it was an incredible feeling to be able to back up my play, my feel, my bad talk… And then to see the video from the bench, JT (Jayson Tatum), Svi (Mykhailiuk), Jaden (Springer), everyone was freaking out after I shot that three, I was like, ‘Man, that’s awesome, man,’ to see the team so excited because I made that shot, it was pretty cool.”