Dodgers pitcher Jack Flaherty throws to an Oakland Athletics batter...

Dodgers pitcher Jack Flaherty throws to an Oakland Athletics batter during the first inning of a game Saturday in Oakland, Calif. Credit: AP/Godofredo A. Vásquez

It’s hard to pinpoint the exact date when the Yankees will regret not trading for Jack Flaherty, the starter they reportedly had in their grasp at the July 30 trade deadline. But the way their rotation has been trending for a while now, that moment feels inevitable.

Fumbling Flaherty -- who ultimately was shipped to the Dodgers, as most deadline prizes typically are -- didn’t seem like a crippling miss at the time, especially with the buzz surrounding Jazz Chisholm’s arrival. But the Yankees’ need for rotation help was undeniable, and even though Flaherty wasn’t the flashiest name floated around, he was the best available, as two-time Cy Young winner Blake Snell and White Sox ace Garrett Crochet never truly hit the market.

There’s nothing GM Brian Cashman can do about that now, other than keep his fingers crossed for the months ahead -- and the healthy return of Clarke Schmidt, who is expected back in September. Problem is, the Yankees’ rotation might be more worrisome at this point than it was at the deadline as their starting corps has been among the worst in baseball for nearly two months, a spiral that continued Thursday night with Nestor Cortes the culprit in the Yankees’ 9-4 loss to the Angels at the water-logged Stadium.

Once again, Nestor was nasty to his own team, allowing six earned runs over 4 2/3 innings, including a leadoff homer to Nolan Schanuel on his fourth pitch of the game. In his last five starts, Cortes is 1-3 with a 9.26 ERA, making him a liability each time he steps on the mound.

“I felt like today was a pretty good command day for me,” Cortes said. “Might have been one or two pitches where I wished to get back, but other than that, I thought I made a lot of good pitches.”

Those remarks don’t quite match up with the results, but Cortes is hardly alone. Since June 15, a stretch of 44 starts, the Yankees’ rotation has a combined 6.26 ERA, which ranks dead-last in the majors. Their 1.49 WHIP was second from the bottom, and their total of 217 innings -- a 4.9 per start average -- is the second fewest in the majors during that span.

That’s no small sample size. And the last time through the rotation, which began just as the deadline wrapped up, didn’t provide much reason for optimism either as Cole (illness) and Marcus Stroman (mechanical issues) were skipped to get right.

Still, when Aaron Boone was asked after Thursday’s blowout how confident he is in the rotation, the manager replied, “very.”

“We have everything we need,” added Boone.

Ironically, the surest thing in the whole bunch, aside from the reigning Cy winner Cole, is probably Luis Gil, who already has blown away his previous single-season high for innings, coming off Tommy John surgery, too. But Gil’s performance data remains strong, despite his three-start swoon in late June, and there is a growing optimism the 26-year-old rookie can pitch well into October.

“I wouldn’t bet against him,” Cole said.

While Gil (12-5, 3.06 ERA) is getting up there in innings, currently at 117 2/3 after Wednesday’s win, his fastball velocity continues to hum along in the high-90s and he looked much sharper at the end of that 107-pitch outing than the beginning. The strategic preservation of Gil has paid off, whether it’s been extra days off or curbing his pitch count when necessary.

The Gil plan has succeeded so far, and could potentially keep him as a viable rotation option for the playoffs. That’s good, because the Yankees are going to need as many choices as they can muster. We’ll assume that Cole should be fine as the No. 1, even though he’s still a work in progress with a 5.09 ERA and Saturday’s start against the Rangers will serve as another mile marker in his return from elbow issues.

“Any time we give the ball to Gerrit, we expect good things,” Boone said. “He’s spoiled us with that certainly.”

For the first two months of the season, the Yankees could say that about the entire rotation as they waited for Cole’s return. Not anymore, as the group stacked behind him has mostly turned precariously unreliable. Rodon, the presumptive No. 2 at a price of $162 million, has been a coin-flip on too many days he takes the mound.

Then there is Stroman, whose own six-start nosedive (7.56 ERA) required him to be sidelined for a mechanical tune-up this week. Since June 28, Stroman has been smacked around at a .355 clip with a 1.000 OPS, averaging slightly over four innings each start and pitching past the fifth just once during that stretch. The Yankees are paying him $37 million through 2025, and Stroman also has an $18 million option that automatically vests if he pitches 140 innings this season (he’s currently at 116 1/3).

“I guess it’s been pretty frustrating,” Stroman said. “But I’m also a realist, and looking at my season as a whole, I can see how good I’ve been in certain spurts.”

The Yankees need more of those from the rotation, top through bottom, to feel better about their AL East title push -- and a deep October run.

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