Rotation turnaround key to stunning homestand

Thursday was 4/20, known as “Weed Day’’ among reefer enthusiasts, and if you predicted in late March the Yankees would be 10-5 after beginning the season 1-4, those drug testers often spotted in big league clubhouses would have asked you to pee in a cup.

Furthermore, if you explained the starting rotation would be the reason the Yankees started Thursday tied with three other clubs for the most wins in the majors, the question would have been: pipe, papers or edibles?

When the Yankees ended spring training, there were big lineup issues. Didi Gregorius was starting the season on the disabled list due to a strained right shoulder. Gary Sanchez wasn’t going to average 10 homers a month for a full season. What did missing a full year mean to Greg Bird? Would Jacoby Ellsbury be better than he was in the first three seasons of a seven-year deal worth $153 million? Aaron Judge?

All of those questions paled in comparison to what smothered a rotation of Masahiro Tanaka, CC Sabathia, Michael Pineda and Luis Severino. Jordan Montgomery was called up on April 12 to make it a five-some.

When the Yankees started the season 1-4, Sabathia was spared the crit- icism because he was the only one of the initial quartet to pitch well. In those first five games, Yankee starters went 1-2 with an obese 7.59 ERA — and that included Sabathia’s five shutout innings against the Rays in the second game of the season.

Now, as the Yankees prepare to open a t hree- game series Friday night against the Pirates in Pittsburgh, which will be followed by three versus the Red Sox at Fenway Park, starting pitching is the reason for the turnaround.

“After the first week, since the first road trip and the entire homestand, the starting pitching has been terrific,’’ general manager Brian Cashman said of a group that entered Thursday’s action ranked seventh among 15 AL teams with a 3.87 ERA and, with an 8-3 record, the most wins in the league. “The starting rotation is a representation of our club.’’

Beginning April 9, when Sabathia allowed two runs in six innings of a come-from-behind win in Baltimore, Yankees starters went 7-1 with a 2.69 ERA. Overall, the club went 9-1.

Sabathia’s second straight strong outing was impressive, but what happened next was stunning. Pineda, more often teaser than pleaser, carried a perfect game against the Rays in the home opener into the seventh inning of an 8-1 victory. That was the second of eight straight Yankees wins.

“We k new they were capable if healthy and if they performed,’’ Cashman said. “We certainly expected that. The past 10 days came to bear that.’’ A 10-5 ledger means there are 147 games remaining before we really know if a suspect rotation in early April was good enough to hurl the Yankees into the postseason. And starting Friday night, the competition — Pirates, Red Sox and Orioles — is stronger than the Rays, Cardinals and White Sox provided on the nine-game homestand during which the Yankees went 8-1.

“I can’t say I’m surprised because I know what they are capable of,’’ Cashman said. “I’m certainly pleased, put it that way.’’