The Pelicans had started last season 4-0 when starting point guard Elfrid Payton injured his ankle. Nothing went right thereafter, including Anthony Davis’ demand to be traded.

Elfrid Payton Sr., a Louisiana native and former star defensive end in the Canadian Football League, believes Pelicans history would have changed had his son not gone down.

Payton played just one game from Oct. 29, when he sprained his ankle, to Dec. 31. After returning from the ankle sprain on Nov. 16, he broke his middle finger in a game against the Knicks.

“I honestly believe if Elfrid doesn’t get hurt and stays healthy, they were making the playoffs,’’ Payton Sr. told The Post in a phone interview from Gretna, La.

As it happened, the domino effect from Payton’s injuries led him to the Knicks. After the season, New Orleans traded Davis to the Lakers, with point guard Lonzo Ball coming to the Pelicans in the deal.

That made Payton a luxury, and he wound up signing a two-year, $16 million deal with the Knicks last month. (The second season is a team option.)

“I think there was interest [from New Orleans],’’ said Payton Sr., who played with seven CFL teams and was elected to the league’s Hall of Fame. “I’m assuming [money] was an issue. But what hurt Elfrid more than anything was the trade. If they don’t trade AD, he’d be here. There was going to be a conflict [with Ball].’’

In stepped an old ally, Knicks general manager Scott Perry. While with the Magic, Perry obtained Payton from Philadelphia on draft night in 2014. Perry has had a yen for the point guard out of Louisiana-Lafayette ever since.

Perry attempted to land Payton for the Knicks at the deadline in February 2018. Payton Sr. ran into Perry at the Garden during a preseason game between the Knicks and Pelicans last October. Perry was asking a lot of questions about his son’s progress.

“I’m very aware of Scott’s interest,’’ Payton Sr. said. “He’s showed confidence in him and always kept track of him when he left. He’s always someone who really believed in him. Somebody invested in you like that and knows you, that’s a big thing.”

According to a source, six teams inquired about Payton, and he also staged talks with the defending champion Raptors, the Hornets and the Pacers.

Perry’s presence with the Knicks — and the notion the starting point guard job was up for grabs — became factors. Plus, Payton is joining the Knicks along with former Pelicans teammate Julius Randle. Payton Sr., who attended every Pelicans home game, said the duo showed “great chemistry.’’

“He chose New York because of the fit,’’ Payton Sr. said. “He’s happy to be on team that has a chance. Nobody is giving them a chance. They’re like the underdogs. They got to grind because they got talent.’’

Resolving their point-guard situation will be a key to whether the Knicks compete for a playoff berth after going 17-65 last season. Dennis Smith Jr. finished last season as the starter. The Knicks are monitoring Frank Ntilikina, who sources said has looked decent with Team France during World Cup exhibitions.

Payton Sr. said he “absolutely’’ hopes his son can start, even alongside Smith, who is less of a playmaker. Payton played 42 games last season and averaged 10.6 points, 7.6 assists and 5.2 rebounds as a starter alongside combo guard Jrue Holiday.

“He’s got leadership to run a team,’’ Payton Sr. said of his son. “Making the right pass, putting people in the right position. He has a talent for finding people and getting the ball where they like it. He’s a true, real point guard. In today’s game it’s interchangeable. Absolutely they can play together.”

A former Grambling star, Payton Sr. said he instilled in his son the desire “not let anyone outwork you.’’ That is one of Payton’s top attributes. The father thinks his perimeter shot is coming along.

A career 30.2 percent shooter from 3-point range, Payton spent May, June and July working on his shot in Los Angeles and now is back in Louisiana.

“His outside shooting has improved every year,’’ Payton Sr. said. “Does it need to get better? Yeah. But every year, it’s improved and free-throw shooting improved. Hopefully this year it will make another jump. He works at what he does.’’