Eight days earlier, Georgia Tech claimed the biggest victory of Brian Gregory’s two-year tenure, beating No. 6 Miami in Coral Gables. That was encouraging. Everything thereafter was less so.

On Saturday, the Yellow Jackets lost at Boston College by two points on the road. Tech is more talented than BC, but such can’t-stand-prosperity losses happen. What transpired here Thursday was far more alarming: Having just seen what Boston College could do, the Jackets turned around and lost by 20 on a neutral floor.

Such a regression is steeped in illogic. A second look at a stylized team such as BC should yield a better effort, not a worse one. But that, sad to say, will serve as the signature of GT in Year 2 under BG — for all the strides taken in the climb from 11-20 to 16-15, there were a slew of missteps.

“When things were going good, we haven’t always responded to that,” Gregory said, speaking after his Jackets lost 84-64 and were eliminated from the ACC tournament two hours after it started. “Because of immaturity, our guys were better at getting off the mat than when they were on top of the mountain.”

In Thursday’s wild mood swing of a game, Tech led 15-0 after five minutes and trailed at the half. After those first 15 points, the Jackets would be outscored 75-35 over the next 29 1/2 minutes. In that dizzying span, the entire Tech team was outscored 38-35 by one BC freshman.

Olivier Hanlan, the greatest Canadian-born scorer since Wayne Gretzky, missed his first two 3-pointers. He made the final eight. He finished with 41 points, establishing a tournament record for freshmen and coming close to the record — 45 by North Carolina’s Lennie Rosenbluth in 1957 — for anyone of any age. And how, you’re asking, does what had been a stout Tech defense turn a rookie into David Thompson?

Said Gregory, measuring his words: “We went to a no-help defense. We weren’t supposed to leave him, but we still had a propensity to leave him.”

Maybe this shouldn’t have been so surprising. When you fall as far as Tech did in the final days of Paul Hewitt, you don’t rise overnight. Last season ended with the regrettable 54-36 ACC tournament loss to Miami in Philips Arena, but that was simply the inevitable ending of a program in the early throes of transition.

This season was much different and mostly better. Tech beat Saint Mary’s, Virginia and Maryland, and then it upset Miami. And then, just when it seemed a corner had been turned, a brick wall wearing BC colors arose.

Said Gregory, smiling: “I’d like to eliminate all those moments where I get hit in the head. We’ll get to the point where I don’t have to duck.”

Maybe the Jackets will. Gregory’s Dayton teams were good at defense and rebounding, less good at running a pretty offense. (Tech fans can already relate.) But his mentor Tom Izzo proved that such a meat-and-potatoes approach can yield banner results, and the Tech roster — three freshmen started Thursday — is much beefier than the one Gregory inherited. What the Jackets are still thin is on the nuances.

There was no on-the-ball defender to check Hanlan, no with-the-ball creator to stop Tech from rushing when the BC rally commenced. Of the Eagles, an admiring Gregory said: “Those guys get in their (offensive) stuff every single time.” The Jackets’ offense wobbled all over creation. Shots that came easy early became too rushed, too rash.

Said freshman wing Marcus Georges-Hunt: “When we were losing, we started to speed up. We got out of our game.”

Gregory: “We at times lack a great moxie or understanding of what needs to happen at a particular time.”

As ugly as it was, this ending wasn’t a program-crusher. Rebuilding is never without potholes. Said Gregory: “It’s been a challenge for us to compete at that (high) level for 40 minutes; the next step — going from competitive to good — is a hard one.”

In a way, the best thing that happened to these Jackets also was the worst. Perhaps some among them thought such a rousing victory meant they had arrived, that modestly gifted Boston College would pose no problem for a team capable of felling mighty Miami.

“If that’s the case,” Gregory said, “that’s disappointing. Who are we to say that?”

The Jackets are nobody special just yet, and they played like nobodies for the final 35 minutes Thursday. Given a bit more time, they could and should be better. Next season will be of massive significance. If March 2014 doesn’t find Tech at least on the NCAA bubble, something will have gone wrong.