ORLANDO, Fla. (AP) Boston's Jayson Tatum opened the Utah Summer League and his pro career with a go-ahead basket to beat No. 1 pick Markelle Fultz and Philadelphia.
The game in Salt Lake City was the most anticipated contest thus far, as summer play heated up Monday with the Orlando Pro Summer League entering its third day and the Utah Summer League tipping getting started. The 24-team NBA Summer League in Las Vegas starts on Friday.
New York, Oklahoma City, Orlando, Dallas, Indiana and Miami were in action in Orlando on Monday. Boston, Philadelphia, Utah and San Antonio got going in Salt Lake City later on Monday.
A look at some of the notable action:
Tatum's jumper and the Celtics' ensuing stop of Fultz gave Boston an 89-88 victory.
Fultz played well on both ends of the floor and showed why the 76ers took him with the top pick they acquired from Boston. Fultz finished with three blocks, including a weakside swat of Kadeem Allen that had the crowd gasping. He had 17 points on 6-for-16 shooting, including two 3-pointers.
''People have big expectations but, to me, it was just another day to play basketball and do what I love,'' Fultz said. ''I love chasing down blocks and blocking shots. On defense I'm always going to give effort on both ends of the floor. That's one thing that goes unnoticed is just how hard I play on both ends. I'm a great shot-blocking point guard.''
Tatum was not overshadowed as the 6-foot-8, 208-pounder showed the versatility he's known for and knocked down a pull-up jumper with 5.7 seconds left. Fultz's shot was blocked on the other end to end the game.
Tatum, the No. 3 pick, may have had the most awe-inspiring play of the night with a thundering, one-hand tomahawk dunk on Kaleb Tarczewski. He posted 21 points, seven rebounds, three assists and five steals.
''He kind of has this old soul,'' Celtics coach Jerome Allen said. ''This pro-like approach, doesn't get rattled, doesn't show a lot of emotions. Just kind of plays at his pace like he's been here before.
''We can say it's only Summer League, but he just made plays.''
While all eyes were on the two rookies, 2016 No. 3 overall pick Jaylen Brown was hands down the best player on the floor and looked like he had no business playing Summer League games. He finished with 29 points.
Brown has taken Tatum under his wing since he joined the team.
''Jaylen can help him with a lot of things,'' Celtics coach Brad Stevens said. ''They've been in the gym a lot together. They've been working out together. I know Jaylen's picked him up and taken him to the practice facility a few times.''
Indiana Pacers first-round draft pick T. J. Leaf showed that his impressive debut wasn't a fluke by following that performance up with an even better second game in Orlando.
Leaf improved on Sunday's 12-point debut by scoring 19 points and grabbing 10 rebounds to help lead the Pacers to an 86-83 win over Miami to move them to 3-0. The 6-foot-10 forward from UCLA, who missed the Summer League opener on Saturday to attend a family wedding, showed some versatility with scoring on the perimeter and in the paint while converting 9 of 17 from the field in 28 minutes.
Joe Young finished with 17 points and six assists, while Jarnell Stokes added 14 points and Chris Johnson contributed 12.
Miami's first-round pick Bam Adebayo led all scorers with 29 points and grabbed 11 rebounds in nearly 32 minutes.
The Dallas Mavericks found themselves quickly in a 17-point hole against Orlando during Monday's game.
They recovered in the second quarter and then separated in the third on the way to an 86-76 win. Dallas improved to 2-0.
Guard Dwight Buycks led the Mavericks with 20 points, while forward Brandon Paul added 18.
No. 6 overall pick Jonathan Isaac had eight points in the first quarter but hurt his hip on a collision in the second and didn't return in the second half.
Point guard Marcus Georges-Hunt, who was called up from the D-League by the Magic in April, contributed 20 points but he had little help.
Knicks rookie Frank Ntilikina has missed the first three games with a knee injury.
It's unclear whether the No. 8 overall pick will participate in Summer League play. Knicks coach Jeff Hornacek did not talk to reporters following the game.
New York dropped to 0-3 after Monday's 99-87 loss to Oklahoma City.
Chants of ''Gordon Hayward!'' broke out in the stands early in Salt Lake City, confirming that minds are on the Jazz All-Star. Hayward, an unrestricted free agent, met with the Jazz in San Diego on Monday, the Celtics on Sunday and the Heat on Saturday. Celtics president Danny Angie and Stevens were both in Salt Lake City to watch Summer League.
Hayward is one of the marquee names in free agency this year and is expected to command a maximum contract.
EX(UM) GONNA GIVE IT TO YA
Jazz Summer League coach Alex Jensen said Dante Exum needs to be heads and shoulders above the competition during the session as he enters his fourth year in the league. The 2014 No. 5 overall pick has yet to find his groove in the NBA, partially due to a torn ACL that cost him all of 2015-16.
No other lottery pick from the 2014 or 2015 is playing in Orlando or Salt Lake City.
Exum certainly stood out in the first half with strong drives to the basket and decisive offense. He looked quick and confident, but faded into the pack as the game went on. Exum finished with 23 points, six rebounds and five assists.
Jensen said Exum played well for the most part, but there were times where he disappeared and struggled to play through fatigue.
''Sometimes I kind of took that step back and wasn't thinking at that moment,'' Exum said. ''I just need to make sure I focus 100 percent of the time I'm on the court.''
PRIDE OF LOUISVILLE
Donovan Mitchell, the No. 13 pick of the draft, showed explosive athletic ability. He was quick enough to get to the rim and even knocked down three 3-pointers, which was not his strong suit in college. Mitchell finished with 22 points on 10-for-17 shooting, five assists, three steals and two rebounds.
The Jazz traded the No. 24 pick and former lottery pick Trey Lyles for the Louisville guard.
AP Sports Writer Kareem Copeland in Salt Lake City contributed to this report.
More AP NBA: www.apnews.com/tag/NBAbasketball