The four biggest questions facing the Celtics heading into the preseason finale

The Celtics’ preseason is almost complete, ending with a final friendly in Toronto on Tuesday. Opening night against the New York Knicks – and the associated banner raising/ring ceremony – follows a week later.

With nearly every player from last season’s championship team still on the roster, we don’t know much about Boston’s 2024-25 squad other than whether it has what it takes to become the NBA’s first repeat champions in six years.

But a few questions remain as the Celtics prepare to defend their title.

1. What role does Al Horford play?

The only Celtics players who have not yet seen the field this preseason are rehabilitating center Kristaps Porzingis, who is expected to miss at least the first month of the regular season as he recovers from leg surgery, and top backup Horford .

Head coach Joe Mazzulla said the 38-year-old big man is not injured but is simply “ramping up” ahead of his 18th NBA season and that he will play against the Raptors on Tuesday. But his use so far raises the question of how exactly Mazzulla plans to use his most experienced player this season.

Horford certainly won’t see the same workload as he did in the 2024 playoffs, when he started the final 15 games after Porzingis’ initial injury and averaged more than 30 minutes a night. He hasn’t played for the second night in a row in several years and will need to manage his minutes to avoid missing out early in the season.

Could Mazzulla decide to bring Horford off the bench even if Porzingis is unavailable? He hasn’t ruled it out, and his understudy Luke Kornet has played well with Boston’s top team this preseason, most recently scoring 15 first-half points in a 50-point win over an undermanned 76ers team on Saturday.

“He worked really hard this summer and I definitely saw him get better,” Mazzulla said of Kornet, who is coming off his best pro season.

Xavier Tillman (more on him below) and Neemias Queta will also factor into the Celtics’ plan to replace Porzingis.

2. Is Jordan Walsh a rotation player now?

After a forgettable rookie season spent largely in Maine and a poor showing at the Las Vegas Summer League, Walsh has been a pleasant surprise this preseason.

Last year’s second-round draft pick looks more comfortable, shoots the ball more efficiently (48.1% field goal percentage; 37.5% from three) and has performed well as a defender and rebounder. On Sunday against Toronto, he posted a double-double with 16 points and 10 rebounds, starting and playing 30 minutes while Boston gave its starters a break.

Walsh was also part of the Celtics’ second unit for both games in Abu Dhabi and saw plenty of playing time with reserve players like Payton Pritchard and Sam Hauser.

“Just understanding what his job is: defending at a high level, defending multiple positions, rebounding and then reading on offense. So he’s doing a great job,” Mazzulla said. “Just really proud of his growth. … (He) is starting to develop a role and develop a really good attitude towards it. So it’s been fun watching him grow.”

Walsh won’t overtake a returning player on Boston’s crowded depth chart, but the offseason departure of Oshae Brissett freed up a spot at the bottom of the rotation. So far, Walsh – who at 20 is still the youngest player in last season’s extended squad – appears to be the favorite to take the youngsters.

3. Will Lonnie Walker IV make the team?

In all likelihood, probably not. Walker has an Exhibit 10 contract — essentially a training camp tryout contract — and with the Celtics well above the NBA’s luxury tax threshold, signing him permanently would cost nearly $10 million in tax penalties, even with a veteran contract. Minimum salary. The more likely path for Brad Stevens and Co. is to leave the final spot on the 15-man roster vacant.

However, Walker has played well in the last two games after seeing minimal playing time in Abu Dhabi. The 25-year-old winger had nine points (4 of 7), seven assists, four rebounds, two steals and a block in 25 minutes off the bench on Saturday. Then he took off and scored 20 points on 8 of 15 shooting on Sunday, scoring from distance and with creative finishes around the basket.

Mazzulla said Walker has been “really good” since his arrival and praised his patience and willingness to learn despite his less than desirable contract situation.

“I saw some things from him (on Saturday) that maybe he doesn’t think is important or others don’t think is important, but they’re really, really important things, both defensively and offensively,” the coach said. “Whether it was his positioning or whether it was a little cut he made or an interpretation he made, those things contribute significantly because they open up possibilities.”

The Celtics’ financial constraints could push the seventh-year veteran to the G League — where he hasn’t played since his rookie season in 2018-19 — but he will have one final chance to prove his worth on Tuesday night.

4. Is Xavier Tillman’s 3-point improvement sustainable?

Despite hitting a memorable three-pointer in Game 3 of the NBA Finals, outside shooting was never a strength for Tillman, who was traded to the Celtics before last season’s trade deadline. In his four NBA seasons, the 6-foot-2 player has made just 26.7% of his three-pointers while attempting fewer than one per game.

That has changed in the last few weeks. In three appearances this preseason, Tillman is shooting a remarkable 80% (6 of 8) from distance, demonstrating a previously untapped aspect of his skills. He can’t expect the success rate to be anywhere near that high over the course of a full season, but even increasing his 3-point percentage to the mid-30s would be a big improvement – and an important one for Boston, like it’s trying to replace Porzingis’ rare blend of rim protection and perimeter shooting.

“He just does a great job and is crucial,” Mazzulla said. “His shot selection, his spacing and his pick-and-roll stats – he’s worked really hard in the offseason and just become more versatile and the player development team has worked really hard on that and that’s a credit to them.”He’s playing really good and I really like how much time he puts in.”

It was notable that Tillman, along with Kornet and the Celtics’ starters, sat out Sunday night’s win. Expect him to play an important role early in the season.