The Duke Blue Devils celebrate their 75-69 win over the Notre Dame Fighting Irish in the championship game of the ACC tournament at the Barclays Center in New York City. (Al Bello/Getty Images)

On the final inbounds play that mattered, above the din that swirled about Barclays Center, Matt Jones subtly yelled. One word: “Jay.”

With that, Jones, a senior role player, took the ball from an official near midcourt. Simultaneously, Jayson Tatum — the Jay in question — snuck behind the Notre Dame defense. How a 6-foot-8 gazelle can slip into a lion’s den unnoticed is something the Irish might still be trying to figure out. Jones flicked the ball downcourt.

Tatum, a freshman, slammed it home and was fouled. And with under half a minute left, Duke had two things of varying value: a five-point lead, and its 20th ACC tournament championship.

Tatum, who has rapidly inserted himself into the best-player-in-the-country discussion, led Duke with 19 points and eight rebounds, including some of the most important plays in the Blue Devils’ 75-69 victory over the Irish in the championship game Saturday night in Brooklyn.

His play in the final two minutes — a free throw that gave Duke the lead for good, a full-court drive, and the jam from Jones — helped the Blue Devils survive what might have been a legendary effort from Notre Dame forward Bonzie Colson, who scored 29 points and grabbed nine boards in nearly willing the Irish to their second ACC title in three seasons.

Yet that little play between Jones — playing in the 141st game of his career, a résumé that includes a national championship — and Tatum shows how far these Devils (27-8) have come in the past two months. By all accounts, this Duke season has been disjointed, and at so many points in January and February it seemed destined for disappointment. Tatum and fellow freshmen Harry Giles missed eight and nine games, respectively, with injuries. Coach Mike Krzyzewski was out with back surgery. At one point, the Blue Devils were 2-3 in the ACC.

Now, these same Blue Devils have their first ACC title since 2011. No team had won an ACC title by winning four games. But Duke — the preseason No. 1 in the nation, but the ACC tournament’s fifth seed — did just that. The Blue Devils arrived at Saturday night because they beat Clemson (expected), Louisville (plausible) and regular season champ North Carolina (something of an upset).

“These last three teams, all of them are Final Four teams,” Krzyzewski said.

There was, too, substance in those results. For what amounts to the first time all year, Duke appears to have its full complement of players performing with both health and confidence. “We’re getting better,” Krzyzewski said after the Blue Devils came from 13 down to beat North Carolina, which had handled them in Chapel Hill six days earlier.

Notre Dame had to play one fewer game to reach Saturday night, but the Irish were impressive in handling both Virginia and Florida State, the second seed, with relative ease. They won this tournament in 2015, putting them in a tiny, two-member club: Schools who joined the ACC since the turn of the century — a group that includes Syracuse and Louisville — to win the ACC tournament.

Duke won the only meeting between the teams during the regular season, and when it twice led by nine in the first half, it seemed like a repeat performance was in the offing. But Notre Dame trailed by only four at the break, and when Rex Pflueger hit a three-pointer less than three minutes into the second half, Notre Dame led for the first time all night — a lead that grew to eight with 11:35 remaining.

But Duke, which used only seven players, somehow found the energy to come back. Down six with nine minutes left, the Blue Devils went on an 11-2 run to take back the lead.

And then, the two plays that won it: Tatum, in the half-court set, unable to find his own shot instead looked to Jones, who nailed a three-pointer with 49 seconds left, making it 71-67. And then, that little bit of communication, from senior to freshman, Jones to Tatum — the play that not only sealed a championship, but showed there might be reason to watch this group during the next three weeks.