Boston Celtics’ Tacko Fall drives into Memphis Grizzlies’ Bruno Caboclo during the first half of an NBA summer league basketball game Thursday, July 11, 2019, in Las Vegas. (AP Photo/John Locher) AP

Among the more popular players from the recently completed NBA Summer League, Tacko Fall made a big impression with the Celtics – big enough to entice them to sign the 7-foot, 6-inch center to a contract for the 2019-20 NBA season.

The Celtics announced Thursday they’ve signed Fall and guard Javonte Green, and also reached agreements with guards Tremont Waters and Max Strus on two-way contracts.

A native of Dakar, Senegal, Fall played four years at the University of Central Florida where he averaged 10.1 points, 7.7 rebounds, and 2.4 blocked shots over 115 games. The 23-year-old competed on Boston’s summer league squad, where he averaged 7.2 points, 4.0 rebounds, and 1.4 blocked shots in five games.

“He’s a great kid, he’s working really hard,” Danny Ainge recently said. “We want to take his development very very seriously. He’s a high priority for us to try to really develop into a player.”

That development will also, partly, be an evaluation. His summer league success was fine, but what can he do against real NBA players. What will he do when he’s faced with guarding good basketball players or defenses that aren’t a hodgepodge of fringe NBA players? Will he still be amusingly effective?

“Tacko is fun to watch. He makes me laugh,” Ainge said. “Some of the plays he makes are hilarious because you just don’t see them. Guards get in a bind and they just throw the ball up in the air, then Tacko grabs them and makes tip-toe dunks from under the basket. It’s just like a senior in high school playing against fourth graders sometimes out there.”

Green, 26, most recently played competitively with Ratiopharm Ulm in Germany. He played in all five of the Celtics’ summer league games, averaging 10.8 points, 4.8 rebounds, 2.8 assists, and 1.8 steals.

Waters was selected by the Celtics in the second round (51st overall) in this year’s NBA Draft. Strus, 23, joins the organization after spending two years at DePaul University.