On the afternoon of Jan. 28, the world opened up with possibility for Georgia Tech. After upsetting then-No. 14 Notre Dame at McCamish Pavilion on Josh Okogie’s stunning buzzer-beating layup, Fighting Irish coach Mike Brey declared the Yellow Jackets an NCAA tournament team, a statement that would have been ridiculous only a month earlier.

Tech was 13-8 overall and 5-4 in the ACC. The second half of the ACC schedule appeared considerably lighter than the first. It was no stretch to believe Brey’s assessment had merit.

“If the tournament is (Jan. 28), we’re in and there’s no question about it,” Tech coach Josh Pastner said. “There’s still a lot of games left.”

A month and a half later, Pastner appears prescient. The Jackets lost their grip on a possible NCAA bid by losing five of their past seven. Overall, the season hardly rates as a disappointment. Pastner was named ACC coach of the year, center Ben Lammers was named second-team All-ACC and defensive player of the year and guard Josh Okogie was selected to the all-freshman team. After Pastner himself was hopeful that Tech would win one ACC game, the Jackets are 17-15 and 8-10 in the ACC. They will learn Sunday if the season will continue with an NIT bid.

What caused the slight slip for the Jackets? Here are five reasons.

Rematches were tough

Tech coaches designed their offensive and defensive schemes to be unconventional, looking for an edge anywhere they could find one. It has worked. Multiple coaches in the conference have noted that the Jackets are difficult to prepare for, particularly Tech’s mix of defenses.

That being the case, it would stand to reason that opponents would be better able to handle Tech’s tactics the second time around, and the results would indicate as much. Against the five teams that Tech played twice — Clemson, N.C. State, Notre Dame, Syracuse and Pittsburgh — the Jackets were 5-0 in the first meetings and 0-5 in the second.

Undoubtedly, part of the reason for the flip-flop is that four of the five first meetings were at McCamish and the rematches were either on the road or at the ACC tournament (Pittsburgh), where the Jackets didn’t play as well.

However, in all five games, Tech’s effective field-goal percentage (which weights 3-point baskets proportionately) went down from the first game to the second, and its opponents’ rate went up.

Abdoulaye Gueye’s injury

The sophomore forward’s ability and confidence and Pastner’s trust in him were growing when he fractured his wrist in the loss at Clemson on Feb. 1. It’s not as though he was an essential difference-maker. In fact, Pastner didn’t play him at all against Notre Dame in the game before the injury. But his improvement was clear, and he was showing an ability to bang around on the inside and get rebounds well enough to give Ben Lammers short rests without risking too much of a dropoff.

Gueye played 18 minutes against Louisville, 10 in the first game against Clemson, eight against Florida State and nine in the second game against the Tigers in which he suffered the injury.

Without Gueye, Pastner wasn’t confident enough in backup Sylvester Ogbonda to spell Lammers consistently. Lammers wasn’t exactly coasting before Gueye’s injury — he averaged 36.3 minutes in the 10 ACC games through the Clemson game — but Pastner maxed him out after that.

In Tech’s past nine ACC games after Gueye’s injury, Lammers averaged 37.2 minutes, including three games in which he played all 40 minutes and three more in which he played 39. Toss out the Wake Forest game when he played only 26 minutes because of foul trouble, and the average is 38.6.

Credit to Lammers, the ACC defensive player of the year, for having the selflessness and toughness to handle it, but he would have been a more effective player with a little bit of rest.

“They look so tired,” Pastner said. “I just think we maybe ran out of gas as we were coming down the homestretch.”

Sickness and injury

After the win over the Notre Dame, Heath was wiped out by a bug that required him to take an IV before he played at Clemson. He was clearly not the same player in the loss to the Tigers and the ensuing loss to Wake Forest. Ogbonda had the same bug before the Wake Forest game.

Forward Quinton Stephens (ankle), Okogie (knee) and Lammers (ankle) didn’t practice before the Miami game with injuries and Stephens and Lammers were clearly limited. Guard Tadric Jackson also fought through an ankle injury.

No team makes it through a season unscathed from a sickness/injury standpoint. However, for a team as thin as Tech has been depth-wise, its string of maladies and particularly the concentration of them time-wise, was punitive.

“It’s not having 13 guys,” Pastner said. “It’s just being able to get into a seven-, eight-man rotation so you can rest some guys.”

Form holds

The second half of Tech’s ACC season didn’t have the big upsets of the first half. But that’s the thing — they were big upsets. The wins over North Carolina, Florida State and Notre Dame were results that, from a probability standpoint, were unlikely to be duplicated. The only other team in the league to beat those three teams, who took the top three seeds in the tournament, was Duke.

Of the final nine regular-season ACC games — home games against Boston College, Syracuse, N.C. State and Pittsburgh and road games against Clemson, Wake Forest, Miami, Notre Dame and Syracuse — perhaps only the N.C. State loss went against expectation. The loss to Pitt on Tuesday could be considered an upset, but the Panthers were actually favored by oddsmakers.

The five teams that Tech played on the road in the second half were 27-13 at home in league games, not counting their games against the Jackets. Clemson, the relative dud in the group, lost at home at North Carolina, Virginia, Syracuse and Florida State by a combined 11 points.

Tech was good enough to steal any of the final five road games, but a variety of reasons, including sickness and injury, fatigue and the opponents simply just being better and being at home, helped prevent it from happening.

Unable to adjust

Beyond just the five opponents that Tech played a second time, the rest of the league got a better bead on how to defend the Jackets. Tech’s cutting game that opened up backdoor cuts for dunks and easy layups — most memorably, Okogie’s emphatic dunk against North Carolina on a seeing-eye bounce pass from Heath — seemed to be less effective as the season went on as teams became more wary of it. Also, Pastner said after the tournament loss, the Jackets’ explosiveness in making those cuts waned.

“I probably have never seen it this packed in on teams, whether I’ve coached or even seen,” Pastner said. “It’s just not normal to pack it in as much as they do.”

With the lane clogged, Tech 3-point attempts accounted for 28.1 percent of all field-goal attempts in the final 10 ACC games, where it was 23.4 percent in the first nine games. It was not a helpful shift for the Jackets. Tech has not shot many 3-pointers (its average of 13.5 per game ranked 349th out of 351 teams on Thursday, according to teamrankings.com) for a reason; the Jackets are 298th in the country at 32.1 percent in 3-point field-goal percentage.

Worse, Tech made 37.1 percent of its 3-pointers in the first nine ACC games but then 29.7 percent in the final 10.