The first regular-season game for the Giants is Sept. 13, and they certainly want playmaking wide receiver Malik Nabers on the field at MetLife Stadium, running routes against the Cowboys in the “Sunday Night Football” opener.

Nabers, though, continues to battle through a strenuous rehab, and for the first time someone in the know is speculating he might not be ready for Week 1.

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“It’s just impossible to predict,” head coach John Harbaugh said Thursday after putting his team through organized team activity practice No. 3. “The goal is to start the season and get out there sometime in training camp, that would be the goal. And we’ll see what happens. If he’s out there, great. If he’s not out there, great, we’ll be ready to go either way. I know he’s fighting like crazy to do his best to be out there. He’s with the guys every day.”

Nabers went down in Week 4 last season with a torn right ACL, and he also suffered meniscus damage in the victory over the Chargers — quarterback Jaxson Dart’s first NFL start.

Nabers had reconstructive surgery Oct. 28 but scar tissue developed, and not long ago he underwent a cleanup procedure.

The 22-year-old receiver is not close to getting back on the field with his teammates this spring.

“Yeah, he’s in the middle of it,” Harbaugh said of Nabers’ rehab. “It’s such a hard thing. It’s an ACL and whatever else he had on that knee. Not a simple knee. He’s in the slog of it, the grind of it, I would say, so he’s fighting through it. He’s here every day working hard at it.”

Indeed, Nabers was in the weight room after the Giants moved practice into the field house because of rain.

Darius Slayton walked into the field house to observe.

The 2019 fifth-round pick and longest-tenured Giant underwent offseason sports hernia surgery and is missing spring on-field work, but Harbaugh expects him ready for training camp.

Without Nabers and Slayton, there are more reps and routes for several newcomers looking to find a connection with Dart.

The Giants in free agency signed two veteran receivers, Darnell Mooney and Calvin Austin III, and also tight end Isaiah Likely, an extremely capable pass-catcher.

In the draft, they traded up into the third round to take Malachi Fields from Notre Dame.

“They’re just dudes who are just bought into the grind and into what we’re doing here,” Dart said.

Mooney, a six-year veteran, spent his first two NFL seasons with the Bears when Matt Nagy was the head coach in Chicago.

Mooney had his career-best production in 2021, catching 81 passes for 1,055 yards, in Nagy’s offense and he is familiar with many of the plays and nuances as he learns the Giants’ playbook, with Nagy as Harbaugh’s offensive coordinator.

Mooney signed a one-year contract for $3 million.

He said he is “an observer guy. I’m usually a slow-motion, slow-burn guy, I would say. I’m always feeling guys out.”

Asked how he sees himself fitting in with the offense, Mooney said, “My role is to make plays and dominate.”

Austin made one of the plays of the day Thursday with a deep catch on the right side on a Dart pass for a touchdown.

Normally a slot target, Austin in three years with the Steelers had 84 receptions for 1,100 yards and eight touchdowns.

“I’m excited about those guys,” Harbaugh said of Mooney and Austin. “They’re pros, starters, established starters in the NFL, and they look good. I think [Dart] is going to feel good about those guys.”

The Giants would like to feel good about Nabers getting back on the field.

It continues to be a waiting game.

Asked how Nabers is handling this lengthy process, Harbaugh said, “I can’t speak for him. It’s probably the first time he’s been hurt like this. My experience with guys, the first time you have a serious injury, it’s tough, because it’s new for him. It’s a tough process.

“Our job is to stay close to him and stay with him, and his job is to trust and work hard. He’s doing his job, and the trainers and docs are doing their job, and he will be back.”

Nabers in four games last season had just 18 receptions for 271 yards and two touchdowns.

As a rookie, he showed the talent that made him the No. 6 overall pick in the 2024 draft, hauling in 109 passes for 1,204 yards and seven touchdowns.

“I think an ACL is a tough injury, especially for a skill player,” said left tackle Andrew Thomas, who was limited to just six games in 2024 after Lisfranc foot surgery. “There is no rush. Make sure he does everything. When he’s 100 percent, obviously he’s a game changer.”