Perhaps the only thing more unlikely than the Giants being in first place in the NFC East heading into their bye week is how they got there.

John Harbaugh was expected to make a difference in his first year at MetLife Stadium, but not like this.

Not with Devin Singletary, an afterthought for much of the season, ending Sunday’s win in Houston with a 30-yard touchdown run. Not with Jameis Winston — thrust into the starting role when Jaxson Dart was lost for the year with a knee injury in the second week of the season — now back in a backup role and still rushing for a score against the Texans.

And certainly not with J.J. McCarthy leading the way as the team’s new quarterback after his career appeared to be going nowhere in Minnesota, which drafted McCarthy 10th overall in 2024.

But here are the Giants, at 4-2-1 and with a clear path to a division title.

It’s McCarthy who has perhaps the greatest chance to alter the trajectory of his career after being shipped to the Giants for a fifth-round pick less than a month ago.

He responded by throwing for 243 yards in less than a quarter when he replaced Winston late in their loss to the Saints, then followed with a career-best 252 yards against the Texans in the same stadium where he led Michigan to a national title in 2024.

“It’s one of those things where you think you’re starting over, but no, you’re starting from experience,’’ McCarthy said of righting himself with the Giants.

He is still only 23 and started just 10 games with the Vikings last season before falling to third on their depth chart behind Kyler Murray and Carson Wentz to start this season.

But he arrived at MetLife Stadium seemingly built for the offense the Giants hoped to run before Dart got hurt.

In their first game of the season against Dallas, Dart and the rest of the offense looked virtually unstoppable.

Dart and McCarthy are not the same player, but they do possess similar attributes and were drafted in the first round just a year apart.

McCarthy was selected four spots behind Malik Nabers and there was no shot anyone would have predicted the pair would be connecting on passes together.

But Nabers has been a huge reason why McCarthy has been so successful so quickly with his new team. In less than five quarters together, Nabers has caught 11 passes for 206 yards from McCarthy.

Nabers, of course, is rounding into form after missing most of last season with a torn ACL. He’s surpassed 100 yards receiving in each of the past four games.

And as much as any team enjoys a bye week, it should be especially beneficial to the Giants, as it will give McCarthy more time to work with his new teammates before they return to action Nov. 8 in Philadelphia.

Despite his struggles with the Vikings, McCarthy said Sunday he began feeling more comfortable in the league in a Week 14 win over Washington. Coming off three straight losses in which he threw six interceptions and just two touchdowns, McCarthy — after missing a week in the concussion protocol — carved up the Commanders on 16-for-23 passing for 163 yards, three touchdowns and no interceptions. He then won his final three starts, though he missed another with a hand injury.

“Just being able to really start feeling like the defense is slowing down and understanding concepts, intent of plays, understanding the situation,’’ McCarthy said. “There’s a lot of things that go into playing NFL quarterback and it takes a little bit to figure those things out. I really feel like I was on an upward trajectory after that game. I continue to just refine my craft and get better every day.’’

He looks to have gotten a solid foundation in Matt Nagy’s offense already, which is why Harbaugh was confident in going with McCarthy against Houston.

For the Giants to continue to build on their success, McCarthy will have to prove he can keep growing as a quarterback.

The early returns, though, are promising — and another example, according to Harbaugh, of a player taking advantage of another opportunity.

“It’s understanding if things aren’t working out for you, that’s not the final say,’’ Harbaugh said Monday. “You have the final say on everything, ultimately.”