Bobby Portis wasn’t going to let his Knicks lose to his old team.

When the schedule came out in August, it was evident the Knicks had rough sledding at the outset. Of the opening six games, their home match versus the Bulls looked like the only winnable game.

As it unfolded Monday night, the Knicks made it very suspenseful, playing an electric fourth quarter behind Portis’ outside shooting to squeeze out a 105-98 win for their first victory of the season.

Portis, who played four seasons for the Bulls, racked up 28 points, and made 10 of 14 shots — 4 of 4 from beyond the 3-point arc. With the fans chanting his name, Portis scored 11 fourth-quarter points in a game the Knicks trailed most of the way, and by as many as 18.

During his first big game as a Knick, Portis turned a couple of times toward the Bulls’ bench and also high-fived Knicks fan John McEnroe in the dying moments. Afterward, Portis admitted he didn’t realize it was McEnroe.

“I’m just an animated player,’’ Portis said. “I play with a ton of energy and toughness. I’m just being myself. I felt I wasn’t myself the first couple of games. I didn’t bring the energy, I had to get back to who I am.’’

Closing with a 15-0 run, the Knicks moved to 1-3 and it was a giant relief to get embattled coach David Fizdale a win.

“We’ve just been waiting for him,’’ Fizdale said. “He’s played a little tight, trying to be perfect. He unleashed it tonight. That was a game.’’

In free agency this summer, Knicks brass spent $74 million for this season and $16 million went to Portis to be center Mitchell Robinson’s backup. Portis had never heard his name chanted in an NBA game before Monday.

“It was fun,’’ Portis said. “I put a lot of work in every summer. To hear the crowd say my name it as a crazy moment for me. It was kind of hard not to hear it.’’

Rookie RJ Barrett also was a factor, scoring 19 points with a season-high 15 rebounds and five assists. Kevin Knox aided the late surge with two 3-pointers and finished with 14 points.

The Garden noise reached a crescendo when Portis hit a 10-footer, then buried a straightaway 3-pointer to tie the score at 88 with 6:04 left.

“That’s the same Bobby Portis I see every day,’’ Barrett said. “He’s a fighter. He willed us at the end to that win, and we’re gonna need him all season.”

The Bulls (1-3) then regained control, going on a 10-2 run, with Tomas Satoransky (drive), Zach Lavine (jumper) and Laui Markannen (3-pointer) stepping up offensively. That put the Bulls in front 98-90 with 3:22 left.

The Knicks went back to work. Barrett notched a three-point play by laying in his own missed free throw. Portis drilled another 3-pointer from up top, sending the Knicks back into the lead at 100-98. Then he added another 3 for good measure.

“I’m disappointed we lost, I’m happy for him,’’ his former Bulls coach Jim Boylen said.
The Knicks got off to an awful start, falling behind 18-6 picking up where they left off in the miserable home opener against the Celtics on Saturday.

“That hurt,’’ Portis said. “It hurts especially at home when someone comes in and smashes you in the mouth and you don’t respond.’’

Fizdale staged an unexpected practice/film session Sunday when the team normally takes off after a back-to-back set.

“He got on our tails,’’ Portis said.

This was hardly perfect and the Knicks will have to be better when they embark on a two-game trip to Orlando (Wednesday) and Boston (Friday).

Julius Randle had another eight turnovers, the club was a horrendous 20 of 32 from the free-throw line, starting point guard Elfrid Patyon hurt his hamstring and Frank Ntilikina went scoreless (0-for-6, including 0-for-4 from 3) despite his gritty defense.

But it was all good in the end. Before the game, Portis met with his former Arkansas coach, Mike Anderson, now at St. John’s and he got revenge on the club that drafted him and traded him in his fourth season.

“The first three games, I didn’t have a rhythm,’’ Portis said. “I don’t really hold any bitter things against the Bulls anymore.”

Ref;nypost.com