Dabo Swinney promised it. Now Clemson can truly enjoy that "biggest pizza party ever."

The Tigers were the No. 1 seed in Sunday’s release of the College Football Playoff pairings, putting Swinney’s 13-0 team against No. 4 Oklahoma in a semifinal Dec. 31 in the Orange Bowl.

On the other side of the bracket, No. 2 Alabama takes on No. 3 Michigan State in the Cotton Bowl, with the two semi winners meeting Jan. 11 in Glendale, Ariz.

Now, for that pizza.

The buffet that Swinney mentioned ahead of the release of the first playoff selection committee rankings — which, like all the ones that followed, had Clemson at No. 1 — was going to happen regardless of the outcome of Saturday’s ACC Championship Game against No. 10 North Carolina.

As the coach told Greenville’s WYFF News days before that game, the Tigers either heading to the playoff or a New Year’s Six bowl "is a great thing to celebrate."

But with Clemson dumping the Tar Heels 45-37, the 81,500-seat Memorial Stadium will be hungry, and for something more than the program’s first national championship since 1981.

For that, Swinney recruited Papa John’s, which was spending five days in preparation to feed thousands, including the Tigers’ Heisman Trophy candidate, quarterback Deshaun Watson, who gave his own order after Saturday night’s win over the Tar Heels, saying "Large pepperoni … with a Sprite. Since we’re not playing (Sunday), I’ll have a Sprite."

Then he and the Tigers will turn their attention to the Sooners for the second straight postseason.

Clemson steamrolled Oklahoma 40-6 in last year’s Russell Athletic Bowl, but it’s a game that should have little bearing on this matchup. That meeting didn’t include Watson or Baker Mayfield, the Sooners’ own walk-on-turned-Heisman challenger of a QB who helped transform the offense.

Watson underwent surgery to repair a partially torn ACL and missed the bowl, and Mayfield sat out last season after leaving Texas Tech for Oklahoma.

The two are second (Mayfield) and 11th (Watson) in pass efficiency at 178.9, respectively, and are both in the top 14 in total offense, with Watson ninth (338.4) and Mayfield 14th (317.4).

They’re both backed by potent running backs as Oklahoma has Samaje Perine (1,291 yards) and Joe Mixon (749), while the Tigers counter with Wayne Gallman’s 1,332 yards.

But the biggest difference between them is on the other side of the ball.

Clemson’s seventh-ranked defense has given up 27 or more points in four of the last six games, including 41 to NC State but it remains fifth vs. the pass (166.9) and only fellow ACC school Boston College is better than the Tigers at stopping teams on third down (24.9 percent).

In the Big 12 where — stop if you’ve heard this before — defenses have been little more than a placeholder to get your offense back on the field, the Sooner faced six units ranked 95th or lower. Out of conference, the best they saw was Tennessee (46th).

So this figures to be the most difficult hurdle facing Bob Stoops’ remade offense, but then again, Clemson hasn’t seen an offense quite like this, either.

The Tar Heels at 11th (40.9) were the only one of its opponents ranked better than 31st in scoring, and of those aforementioned teams that had scored 27 or more vs. the Tigers of late, they included the Wolfpack (38th), Syracuse (77th) and South Carolina (110th).

Since their Oct. 10 loss to Texas, the Sooners have scored no fewer than 30 points, and over a final three-game stretch that included No. 6 Baylor, No. 18 TCU and No. 11 Oklahoma State, they averaged 44 points, punctuated by 58 in a 35-point rout of the Cowboys. That high-powered attack helpd Oklahoma jump all the way from 15th in the first CFP rankings to the final four, just one spot lower than Ohio State was in the opening poll a season ago before it went on a tear en route to winning the title.

While the other semifinal game will be predicated by hard-nosed, winning-the-line-of-scrimmage play, Clemson-Oklahoma has all the makings of providing serious New Year’s Eve fireworks.

And, at least at its announcement, pizza. Lots and lots of pizza.

Follow Cory McCartney on Twitter @coryjmccartney and Facebook