Aaron Boone bounced between his office and the video room at Yankee Stadium and found what he saw on screens in both places revealing and, therefore, thrilling.

From his familiar dugout spot, of course he had noticed how much better Chad Green was pitching, notably since returning from the minors in May, but particularly in the second half. But this was such a worthwhile ejection. Because on Sept. 21 against the Blue Jays he was now able to see Green’s pitches more vividly while locked in on the TVs, and this was his review:

“Oh, wow, that’s a real slider.”

There are many reasons Green has been arguably the Yankees’ best pitcher since the break, including streamlining his delivery in the minors, which brought control and late carry back to his bread-and-butter fastball. But he also exchanged an offset grip that made his breaking ball basically a cutter to one that enabled him to create late break and depth to what he says is “now a true slider.”

When he has that, “The hitters are more between his slider and his fastball, and it just allows his fastball to play up so much more,” catcher Austin Romine said. “It is such a benefit to get it in the mix.”

In that game against Toronto, Green struck out the side on 15 pitches. Nine were sliders. Four were swung on and missed. It was part of a September in which the 28-year-old righty faced 49 batters and whiffed 26. Which sets him up as one of the most important Yankees this October.

Boone announced Thursday he will not use an opener in the first three Division Series games against the Twins, going traditionally with starters James Paxton in Game 1 followed by Masahiro Tanaka and Luis Severino. Yet, Boone indicated he will be proactive, hooking starters without signs of trouble if he sees a preferable pen matchup.

The Yanks have played toward this all year. They are the only team that never used any reliever more than two straight days. The idea was to keep their Big Four — Zack Britton, Aroldis Chapman, Tommy Kahnle and Adam Ottavino — fresh to attack October. But a funny thing happened on the way to this month. This became a Big Five with Green, whose significance only magnified.

Ideally, the Yankees would have Dellin Betances and Domingo German to even better attack the Twins’ righty masher-filled lineup, and German and CC Sabathia to provide pen length. But Betances (Achilles) is out for the year, Sabathia (shoulder) is at least out for this series and German is done for the season awaiting to hear what kind of suspension awaits through MLB’s domestic violence protocols.

So, Green’s Swiss Army knife capabilities only expand in value. He can open, close, throw multiple — or one — relief innings and be summoned with men on base as an elite option to deliver a couple of get-out-of-jail strikeouts.

“I don’t want to put any pressure on him at all, but I think Chad is one of our best pitchers,” Ottavino said. “He’s the one guy that often pitches multiple innings. He has been so dominating his whole career, outside of the beginning of this year. I really believe in him a lot. I really think he can be a huge factor for us in the playoffs.”

Green had a 2.18 ERA and averaged better than 12 strikeouts between 2017-18. And he was one of the pen heroes in the 2017 wild-card game against Minnesota after Severino lasted just one-third of an inning and put the Yanks in a 3-0 hole. He bailed Severino and the Yankees out of a second-and-third nightmare with two strikeouts, and the Yanks reversed momentum en route to an 8-4 triumph.

But in April this season Green was besieged by the homer epidemic, surrendering four in 7 ²/₃ innings. He was demoted to Triple-A. He returned three weeks later, and since then in 44 appearances, including 15 as an opener, had a 2.64 ERA and .653 OPS against.

It is in the second half, though, that Green dominated, holding opponents to a .176 average while striking out 36.7 percent of batters. The highlight was an 11-game (17 ²/₃ innings) final statement in which opponents mustered a .086 average, which included Boone’s favorite TV show.

“I’m in a good place,” Green said. “I know exactly what I’m trying to do. I feel like I am reading swings better. I feel like my breaking ball is better. The past couple of weeks it has felt a lot better. I have been leaning on that a lot more to get guys off of my fastball. In the past, when I didn’t have my fastball, I didn’t have anything else to go to. I didn’t have my breaking ball. Getting more confidence in that pitch was big for me.”