Joe Mazzulla spanned the globe this summer to spend time with his players,arriving in Spain, Portugal, Dallas and Omaha. His most remote happened 20 minutes south of Des Moines, Iowa.
“It was one of the biggest things that’s happened in Indianola in a long time, I’ll tell you that,” Frank Garza, Luka’s father, told CLNS Media/CelticsBlog on the Celtics Daily Podcast last week.
While Mazzulla provided words of wisdom and moral support at one of Garza’s two basketball camps in Iowa, Celtics assistant
D.J. MacLeay visited Garza in his native Washington D.C. for defensive work with Boston’s big man.
Neemias Queta ascending to the starting center role last season and Mitchell Robinson’s arrival in free agency leaves Garza in a depth role entering 2026-27. However, he proved himself as a reliable NBA reserve last season. He averaged 8.1 points, 4.1 rebounds and 1.0 assist while shooting 57.7% from the field and 43.3% from three in 16.2 minutes per game during the regular season.
Like with Queta and Nikola Vučević playing in front of him, foul trouble doomed Garza in the playoffs against Philadelphia, committing 8.5 per 36 minutes compared to 5.2 during the year. That’s why Garza, his father and MacLeay largely focused on that side of the ball in their offseason work.
“(Luka) worked incredibly hard on defense,” Frank said. “We’re talking 90 possessions on defense where he’s either doing drop coverage or screen-and-roll … for a center particularly, 90% of the game you don’t have the ball, thus, you should be practicing 90% without the ball … you’re gonna be boxing out, you’re gonna be defending … that’s how his practices were mimicked … a lot of defensive positions, a lot of handwork, a lot of foot drill work, just to improve upon the things that he needs to continue to do.”
The Garzas also focused on improving Luka’s defensive rebounding after a standout season on the defensive glass. At Iowa and to begin his NBA career, he often boxed-out to allow other players to grab rebounds, which will continue with Jayson Tatum’s return for a full season. They want Garza to have the ability to fight for loose balls defensively more often, with Queta’s 22.7 DREB% finishing far ahead of Garza’s 12.0 DREB%. Robinson posted a 26.1 DREB% as arguably the league’s best rebounder in 2026.
Garza began 2025-26 as Boston’s backup big man before his defensive struggles and the Celtics’ immense issues on the defensive glass led Mazzulla and the coaching staff to lean into rebounding wings like Josh Minott over Garza early in the schedule. They always planned to return to him, but he needed a breather and time to acclimate to the system. Meanwhile, Mazzulla searched nightly for maximum effort from Boston’s bench players while trying to establish a culture.
“You just don’t know when you’re gonna get in, and when you get in, the treadmill’s going 100 miles-per-hour, and you better get in there and … box out every time, you better go and get a rebound every time,” Frank said. “You better do all these things. There’s zero tolerance for any lack of effort. It wasn’t that he was doing a lack of effort, he was slowly getting in the flow of the game and that’s just not acceptable. You have to be ready before you get in the game and that was the big adjustment.”
Despite returning to the rotation in late-December with 9.2 PPG and 5.0 RPG while shooting 46.7% from three in winning minutes across 18 straight appearances, the Celtics ultimately added Nikola Vučević at the trade deadline. Garza initially struggled with the demotion before buying into the bigger picture and awaiting another opportunity that came when Vučević broke his right ring finger in March. Garza scored 10 points that night in a win over Dallas, closed the season averaging 10.7 PPG and poured in the game-winning three starting alongside Boston’s bench players in Game 82 against the Magic starters. He finished with 27 points and 12 rebounds. Frank said they had practiced that shot-fake shot.
Following his surprise spot start in Game 7 against the Sixers two weeks later, where Garza missed both three-point attempts and fouled three times, he continued working on his shot with a greater attention to doing so in game speed and movements. Garza put up perhaps the highest number of practice shots in the league to becoming a reliable threat from deep. Yet he’ll need to draw defenders out more consistently to continue his offensive growth and fit in an as occasional power forward, which Boston briefly tried unsuccessfully after the Vučević trade.
Even if he’s strictly playing the five, opportunities will emerge for Garza. Robinson’s healthiest season saw him play 72 games in 2022, and he averaged 42 in four years since (22.9 MPG). Neither Queta nor Robinson have shot threes in the NBA, and the latter struggles immensely at the free throw line.
Garza received an opportunity to showcase his improvements already with the Bosnian national team after sorting out passport issues that prevented him from participating in the 2025 EuroBasket tournament. He backed-up Jusuf Nurkić, averaged 16.8 PPG and 7.3 RPG, highlighted by 27 points in a win over Türkiye and a 16-point showing against Nikola Jokić and Serbia. Participating in the World Cup qualifiers marked a life-long dream for Garza, as he continues working toward his larger one of carving out a successful NBA career.
For that, he has Mazzulla in his corner.
“He can keep it very simple about what needs to be done,” Frank recalled from meeting the head coach in Iowa. “The game’s so complex, but he can break it down into bite-size, powerful gold nuggets about player development … and then the fact that you don’t just need to have hard work … you gotta have more than just hard work … you have to add something else, you have to add this intangible, how do you treat your teammates? How do you show it? The reason you talk on defense isn’t just to make noise, it’s to make sure your teammate knows what’s going on.”
Entering Year 2, despite added depth in the center room, expect to hear a lot more from Luka Garza.
