Ben Simmons learned a valuable lesson in his first summer league game: Drink more fluids.

After cramping up in the third quarter of his summer league debut against the Boston Celtics, the Philadelphia 76ers' No. 1 overall pick, who attributed his injury to not playing for the past four months, plans to sit out in Tuesday's game against the San Antonio Spurs.

"It's an adjustment, obviously," Simmons said. "The game is a lot harder, a lot quicker. It's one of those things you just got to stay on it."

Simmons and Jaylen Brown still gave fans a glimpse of their respective talents in the opening game of Monday's doubleheader. Both top-three picks guarded each other all game; Brown finished with 16 points and six rebounds in Boston's 102-94 win, while Simmons finished with 10 points, eight rebounds and five assists.

Even in a July exhibition, there was no question why Simmons' name was called first in the Draft. At 6-foot- 10, he ran the floor like a point guard and dictated the game like a veteran.

"There's going to be a lot of opportunities where I can find guys like I did today," he said.

The former LSU star did a little bit of everything and made it look easy. Simmons even faced up Brown in the first half and smoothly knocked down an elbow jumper.

"Ball handling, confidence, communication, swagger, enthusiasm, love for teammates," Sixers coach Billy Lange said of Simmons. "It wasn't about him. Everyone wants to put a label to it, but he's just a basketball player. He's a really good basketball player … there is still a long journey ahead."

Brown wasn't too shabby himself. Despite taking a little longer to get settled in, the 19-year-old forward from California attacked the rim and exhibited a calmness that contradicted his age. Late in the fourth, Brown got in his groove and showed why the Celtics decided to take him at No. 3.