After a disastrous week for the rotation, the Yankees were set to implement plenty of changes, both large and small.

One of their most important pitchers, though, said “drastic” measures were needed.

That’s why, for the first time in his career, Masahiro Tanaka said he altered the grip on his split-fingered fastball following his nightmarish outing against the Red Sox, when he allowed 12 runs in a loss at Fenway Park.

“I’ve always, up to this point, tried to stick with the grip that I’ve always used for the splitter and made small adjustments in order to get the movement that I want,’’ Tanaka told The Post through an interpreter. “You get good results and bad results and the difference between the two are so big. When it’s good, it’s really good, but when it’s bad, obviously, it’s been very bad. I thought I needed to make a different type adjustment here. That’s the biggest reason I went to something as drastic as changing the grip.”

Pitching coach Larry Rothschild previously said he hoped Tanaka would alter his grip, in part due to the lower seams on the baseball that have helped cause the home-run surge around the majors this season.

Tanaka’s All-Star first half had its fair share of inconsistencies, but he’s had especially bad results against the Red Sox. He failed to get out of the first inning when he faced them in London, and then had a historically rotten start Thursday at Fenway, when he gave up the second-most runs in franchise history.

The issues began when he gave up five runs in the sixth inning in a win over Colorado on July 20 in The Bronx.

Asked if he thought the new grip was effective, Tanaka said he believed it was, but added: “I guess we’ll see.”

That’s how most of the rotation felt heading into a six-game homestand on Tuesday, with the Diamondbacks in town for two games, followed by another four-game series versus Boston.

Depending how the Yankees handle Wednesday’s trade deadline — as well as the rest of their rotation — Tanaka could avoid the Red Sox this weekend, but probably not for the rest of the season.

Domingo German became the first Yankee starter in over a week to complete five innings in their win in Boston on Sunday, but everyone has played a role in how shaky the rotation has been of late.

“We’re trying to attack everyone individually,’’ Aaron Boone said before the Yankees’ 4-2 loss to the Diamondbacks.

He pointed to mechanics, game plans and other tweaks, but the manager also insisted the Yankees weren’t “overreacting” to what they believe has been a short-term issue.

“Everyone had a rough go one time through,’’ Boone said. “The fact it all happened in a week makes it difficult.”

It doesn’t figure to get much easier — at least not on the pitching side, especially with CC Sabathia expected to get an injection in his surgically repaired right knee on Tuesday, which could keep him out longer than a two-week stint on the injured list.

With a pair of doubleheaders slated against the Red Sox and Orioles, the Yankees are set up to play 19 games in 17 days following Thursday’s off day.

“That’s gonna be a tough stretch where everyone in our rotation, everyone on our pitching staff, is gonna have to play a meaningful role and pick up some meaningful innings,’’ Boone said. “Guys have got to pitch well.”