Lonnie Walker IV left a solid impression, both on and off the court, during training camp and the preseason with the Boston Celtics. But once it came down to trimming down the roster for Tuesday’s Opening Night, there wasn’t enough room for him.

Due to the domino effect of Boston’s offseason spending — the Celtics compiled over $500 million in combined extensions — the chances of keeping Walker around were thinning as Saturday’s 5 p.m. ET deadline approached. Walker’s initial $2 million deal with Boston, had the 25-year-old not been waived, would’ve put the Celtics on the hook for another $10 million on top of an already hefty tax bill.

The ultimate trigger was inevitable although, on paper, Celtics president of basketball operations Brad Stevens made the right call in signing Walker to an Exhibit 10 contract. Walker, a six-year veteran, a career-35.6% 3-point shooter and a proven playoff performer, wasn’t the traditional caliber of player you’d find signing a non-guaranteed training camp invitation deal, but it paid off. Boston saw first hand just what Walker could do for the reigning champs, albeit on a small sample size.

The reception spoke for itself during Saturday’s practice at Auerbach Center.

“A guy that’s been around the league a long time and has seen different environments. He came in with his head down and just wanted to work and wanted to have an understanding of what it is to play our style of basketball on both ends of the floor,” Celtics head coach Joe Mazzulla told reporters, per CLNS Media. “I thought he did a good job of executing that in the time that he had and I thought he did a great job being patient, executing the role we needed him to and I thought he did a good job in the film room trying to get to the understanding of our system on both ends of the floor.”

Walker was a surprise name left in the cold and dreary free agency market in late August. He averaged 9.7 points, 2.2 rebounds and 1.3 assists on 42.3% from the field and 38.4% from three, logging 58 appearances (17.4 minutes) for the Brooklyn Nets last season. In the three seasons prior to joining the Nets, Walker averaged 11.7 points across a combined two years with the Los Angeles Lakers and one with the San Antonio Spurs.

When the Celtics called Walker’s number and gave him the nod to start against the Toronto Raptors in their second-to-last preseason contest, Walker delivered. He scored 20 points in 30 minutes and drained each of his first four 3-pointers.

“Great guy, works hard and you can tell he’s got a lot of passion about the game and that’s my guy always,” Derrick White said, per CLNS Media. “I talk to him too much, I think. I try to give him space. I’m just kidding. We’ve been close since he got drafted in San Antonio so that’s my guy and I’m sure we’ll talk soon.”

White and Walker spent three-and-a-half seasons with the Spurs together, both playing under head coach Gregg Popovich. It didn’t take long for White to speak highly of Walker, a longtime friend, once he joined the Celtics and the possibility of the former San Antonio-grown veterans reuniting for Boston’s title defense run hasn’t faded away into oblivion just yet.

Walker now has two options at this point: either join the G League Maine Celtics and await the (expected) promotion to Boston or sign a pro-level contract with another team. Either way, Walker is aiming to bolster his stock value — if an outsider doesn’t sign him to a multi-year contract — before returning to free agency next offseason.

He took to Instagram to share a short, but straight-to-the-point message shortly after Boston’s front office made its decision.

“Will always bet on myself,” Walker posted on his Instagram story. “This is gonna be one hell of a story.”

If it was up to the Celtics locker room, however, the decision would be a no-brainer.

“I love Lonnie. I feel like he’s a great player honestly,” Luke Kornet explained, per CLNS Media. “His energy and just joy and passion and connection that he innately possesses is awesome and I’ve never really had the opportunity to know him closely until these past few weeks and he’s been great to have around. Honestly, just a joy to play with and a joy to work with.”