The fact the Yankees are in firm command of the AL East this far into the season isn’t exactly a surprise.

How they got here, though, certainly is.

The importance of Domingo German and DJ LeMahieu was on display again in the first game of Saturday’s split doubleheader in front of another sellout crowd in The Bronx, as the two led the Yankees to a 9-2 win over the Red Sox.

LeMahieu’s two homers — including a three-run shot in a seven-run fourth inning — sparked the offense, and German delivered yet another strong start as the Yankees knocked off their rivals for a third straight game. It was also Boston’s sixth straight loss.

The Yankees knocked around Chris Sale in the process, something that has also become commonplace this season.

Sale entered 0-3 with a 7.71 ERA in three starts versus the Yankees in 2019 and was even worse Saturday. He allowed a season-high eight runs in just 3²/₃ innings, his second-shortest outing of the year.

German (14-2), meanwhile, outdueled the lefty for the second time in less than a week. He gave up just two runs in seven innings and has allowed more than three runs just once in his last six starts.

Last Sunday, he began the Yankees’ turnaround by stabilizing the rotation after they got beaten up for seven straight games, but he was better on Saturday.

Though the Yankees have said German is on an innings limit, they have yet to say how it might impact the right-hander’s usage down the stretch.

“We’ll obviously start to have those conversations and go accordingly,’’ Aaron Boone said of German’s workload. “We still feel like he’s strong.”

Boone made it clear German will be in their October plans.

“I expect him to be big part of it,’’ Boone said.

The news wasn’t all good for the Yankees, who lost Edwin Encarnacion to a right wrist fracture when he was hit by a pitch from Josh Smith in the eighth inning. He was placed on the 10-day injured list after the first game, with Mike Ford recalled from Triple-A Scranton/Wilkes-Barre.

LeMahieu started the Yankees off with a leadoff homer against Sale. It was his 16th home run of the season — a career high. It was also the fifth allowed by Sale to the Yankees this season.

After Sale (5-11) followed by hitting Aaron Judge, he retired the next seven batters until LeMahieu singled with one out in the third. He was erased on a Judge double play.

The Red Sox tied the game when Andrew Benintendi took German deep to open the second, but the right-hander rolled along. He pitched out of trouble in the fourth, when German struck out Brock Holt and Mitch Moreland with two on to end the threat.

The Yankees got to Sale again in the bottom of the fourth, when they scored seven runs, all with two out.

Three singles loaded the bases with two outs for Breyvic Valera, who singled to right to give the Yankees a 2-1 lead.

Boston manager Alex Cora came out to visit Sale and got tossed by home plate umpire Mike Estabrook after the Red Sox had questioned several of his calls with both pitchers.

Cora’s chat with Sale did no good, as Brett Gardner smacked a two-run single to center and LeMahieu homered for a second time. The three-run drive to the short porch in right put the Yankees up 7-1.

The struggling Judge then ripped a double to left to end Sale’s miserable afternoon.

As he walked off the mound, Sale shouted at Estabrook, who tossed the left-hander despite the fact he was out of the game.