The Celtics waived three players from their training camp roster Thursday, whittling down their group ahead of next Tuesday’s season opener.

Lonnie Walker IV survived that cutdown. When Boston opened its gym to reporters after Friday’s practice, the veteran wing was still there, taking jumpers on the northeast basket alongside a Celtics assistant.

Whether Walker, who’s on an Exhibit 10 tryout contract, could earn the final open spot on the Celtics’ 15-man regular-season roster was one of the biggest questions facing the team this preseason. As of Friday afternoon, it remained unanswered.

That won’t be the case for much longer. Boston has until Saturday to decide whether to cut Walker and have him begin the season in the G League, or add him to the opening-night roster and accept close to $10 million in luxury tax penalties.

Head coach Joe Mazzulla wouldn’t tip the team’s hand during his post-practice news conference, but he commended Walker for his professionalism.

“He had a great training camp,” Mazzulla said. “I liked his attitude. I liked his work ethic. I thought he really got acclimated to our defensive system, and I thought he really worked to study the offensive system and how he fit in. I thought he took advantage of the time that he had, and that’s really all you can ask for.”

After playing sparingly in the Celtics’ first two preseason games in Abu Dhabi, Walker impressed in both exhibitions at TD Garden. The 25-year-old tallied nine points, seven assists, four rebounds and two steals in 25 minutes against the Philadelphia 76ers’ backups, then scored 20 points on 8-of-15 shooting in a home win over the Toronto Raptors.

“I think he’s been really good,” Mazzulla said after the Sixers game. “I think it’s an adjustment coming here because it’s just a different style of basketball, and I like his open-mindedness to learning. I like his patience. It’s funny when you get a guy like him who’s been in the league for seven years.

“I saw some things from him (last Saturday) that he might not think are important, or other people won’t, but they’re really, really important things, defensively and then offensively. Whether it was his positioning or whether it was a small cut that he made or a read that he made, those things go a long way because they open up opportunities.”

Walker did not leave the bench in Tuesday’s preseason finale in Toronto, however, during which Mazzulla utilized a tight rotation for the first 3 1/2 quarters before giving a handful of reserves some late run.

Second-year pro Jordan Walsh, who played 24 minutes in that game, looks like the favorite to take over Oshae Brissett’s end-of-the-rotation role after his surprisingly strong preseason. The only other departure from last season’s Celtics team was Svi Mykhailiuk, who ranked 13th in minutes played per game for the NBA champs.

Walker — a seventh-year veteran with 322 games of NBA experience and a solid track record as a productive scorer — would be an upgrade at that spot. He’s coming off a 2023-24 season in which he appeared in 58 games off the bench for the Brooklyn Nets and averaged a career-high 20.1 points per 36 minutes. The previous year, he was playing meaningful playoff minutes for a Los Angeles Lakers team that reached the Western Conference finals.

But Boston must decide whether it’s worth paying the aforementioned hefty tax bill for a player that far down on the depth chart.

Shipping Walker to the G League, with the chance for an in-season call-up, would make the most financial sense for the Celtics. President of basketball operations Stevens told Walker a stint in Maine was a possibility when the latter signed in late August, and Walker — who hasn’t played in the NBA’s minor league since his rookie year in 2018-19 — said he’d be “perfectly fine” with that outcome.

After his promising outing against Philly, Walker downplayed the pressure of playing on a non-guaranteed contract.

“I don’t really believe in pressure,” he said. “I mean, I’ve been playing this game my whole life, and that all comes with my preparation that I’ve been doing. Being one of the first people in the gym and one of the last people out, coming in at night to get shots up. I’m doing everything in my power to make sure I’m mentally and physically prepared for whatever might be happening.

“If things do go how it’s supposed to do, then I’ll be happy. If it don’t go how it’s supposed to be, then at the end of the day, I can tip my hat off as a man, to understand that I did everything in my power to do what I could.”

Did he do enough? We’ll soon find out.