PITTSBURGH — The Yankees hit the halfway mark of the season Tuesday when they faced the Pirates.

They entered the day with a 13-game lead on the second-place Red Sox in the AL East and their only legitimate challenge in the American League — and it’s a sizable one — seems to be the Astros.

“I thought we had a good chance to be a really good team,’’ Aaron Boone said over the weekend in Cleveland, where the Yankees won another series.

“Any time you have the kind of record we have at this point, I don’t know if you can necessarily predict something like that. Certainly, we’re very pleased with how we’re playing the first half, understanding it’s only that. There’s a long way to go, but we have a lot of confidence that we have a chance to be a really special team.”

“We want to be a championship club,’’ Boone said. “We’ve shown at least that potential exists. Right now, that’s still all it is.”

So what have been the keys to the red-hot first half?

With Jameson Taillon on the mound against his former team on Tuesday, the Yankees will have gotten 77 starts in 81 games out of Taillon, Gerrit Cole and Jordan Montgomery (16 apiece), Nestor Cortes (15) and Luis Severino (14). The only four exceptions came due to doubleheaders and makeup games. And even then, they got solid to above-average performances from JP Sears, Clarke Schmidt and Luis Gil.

Due to innings limitations on Cortes (who will surpass his career-high in workload) and Severino (whose limited workload due to injuries the previous three years will prevent the Yankees from pushing him too hard), the Yankees will need to rely on more arms in the second half. That could come in the form of someone like Schmidt — who is building up as a starter with Triple-A Scranton/Wilkes-Barre — or Domingo German, the right-hander in the midst of a rehab assignment. Another alternative is an acquisition before the Aug. 2 trade deadline.

The only non-COVID IL stints to Yankees regulars were a strained calf from Giancarlo Stanton and a right shoulder injury to Josh Donaldson.

While the rotation has stayed remarkably intact, the same can’t be said for the pen. Chad Green is out for the year with Tommy John surgery, Jonathan Loaisiga has been sidelined with right shoulder inflammation since May 23 — and was largely ineffective prior to the injury — and now Ron Marinaccio, who emerged as a trusted reliever in his rookie season, is on the IL with right shoulder inflammation. And then there’s Aroldis Chapman, who missed time with Achilles tendinitis, but has been dreadful since mid-May. But the emergence of Michael King and especially Clay Holmes has made up for much of that. Left-hander Wandy Peralta has also been excellent and Albert Abreu has shown flashes of what the Yankees had hoped for him for years since his return to the organization after he was designated for assignment.

Despite the inconsistency of Isiah Kiner-Falefa at shortstop, the Yankees have gone from among the worst defensive teams in the league to arguably the best. According to Fangraphs, they lead the majors with 50 defensive runs saved.

A full season of Anthony Rizzo at first base, Gleyber Torres’ comfort at second and Josh Donaldson at third — along with the versatility of DJ LeMahieu and Marwin Gonzalez — have all contributed, as has Jose Trevino behind the plate, where he’s also guided the pitching staff to a stellar first half.

The Yankees didn’t lose last year because of their pitching. It was their offense that mostly let them down. That hasn’t been the case this season — although there have been some worrying trends of late from Donaldson’s struggles to Torres cooling off. Aaron Hicks and, in particular, Joey Gallo, have been woeful.

But Stanton and Rizzo have brought power and LeMahieu has been solid — if not spectacular. Still, it’s Judge who has driven the offense with his torrid first half as he heads toward potential free agency.