How many 50-17 runs do you think the 2003-04 Pistons allowed at home to close out a first half?

One day after David Fizdale used that example of the selfless, starless and defensive-minded team he wants the Knicks to personify this season, they were getting blown out Friday night for much of their first preseason game at the Garden until a too-late surge resulted in a 115-99 loss to the Wizards.

“We stopped guarding the 3. We relaxed,” Fizdale said after his team allowed Washington to connect on 19 three-point baskets. “From Game 1 to Game 2, our closeouts were a nightmare.

“Absolutely we have to be good defensively. I do think we have more scoring this year, but our first priority has to be the defensive end and taking that challenge.”

At least newcomer Marcus Morris didn’t bop anyone on Washington on the head with the ball, as he did to Justin Anderson to earn an ejection in Monday’s win. But the veteran forward did pick up another technical foul early in the third quarter before finishing with a team-high 21 points in 31 minutes.

First-round pick RJ Barrett added 15 points on 6-for-15 shooting in his preseason home debut, and second-rounder Ignas Brazdeikis saw his first action of the preseason but didn’t score in seven minutes.

“They hit a whole bunch of 3’s, and there’s not much you can do when they’re hitting shots like that,” Barrett said.

Fizdale had former All-Star center Ben Wallace address the team during practice Thursday about the 2004 Pistons winning the NBA title without any superstar players on their roster.

Before the game, Fizdale also clarified that he didn’t believe the Knicks played selfishly throughout last season, when several players were headed to free agency. Only occasionally.

“Last year’s team had moments of selfishness. That team was bought in, that team was committed, they played hard, they played together. And they tried to help each other,” Fizdale stressed. “So I just want to make sure, for the record, we understand that.”

“Because I really enjoyed that group of men. They worked hard for me, and I don’t want no narrative out there that those kids were selfish. They all went through moments of selfishness, every team does.”

When asked after Thursday’s practice what he learned from having so many players on expiring contracts the previous year, he had said, “I don’t know. I think what you try to do is you try to stay ahead of it. If you see any kinds of signs of anyone going for self, you nip it early and you address it early. I’ve got a different feeling with this group for whatever reason. I just feel like all of these guys are understanding that the better our team does the better it is for them individually.”

Fizdale has preached a team-first approach with this season’s roster, after stars such as Kevin Durant, Kyrie Irving and Kawhi Leonard spurned the Knicks in free agency in July. The Knicks spread their available cap space — which was enough to sign two max free agents after trading Kristaps Porzingis and others — on seven lower-tier free agents.

The group was headed by $63 million forward Julius Randle, but also included short-term deals with established veterans such as Morris, Taj Gibson, Wayne Ellington and Bobby Portis. All but Randle can become free agents again in 2020.

“They understood that we wanted to keep flexibility but at the same time that doesn’t mean we don’t want them back,” Fizdale said. “A lot of these guys are making great impressions and will have the chance to be back with us next year.”

The Knicks cane out looking sharp, with Barrett netting six quick points, for a 30-15 lead with 2:47 remaining in the first quarter. But the Wizards scored 17 straight points and closed out the half on a 50-17 run, with Bradley Beal registering all 21 of his points before intermission.

“After eight minutes, we just kind of relaxed, let our guard down,” Randle said. “That’s the NBA. They started hitting a bunch of threes and feeling good about themselves. They went on a run and we didn’t respond.”