No. 1-ranked Alabama will return to the Georgia Dome one last time to face No. 4 Washington in a College Football Playoff semifinal in the Chick-fil-A Peach Bowl on Dec. 31.

No. 2 Clemson will meet No. 3 Ohio State in the other semifinal in the PlayStation Fiesta Bowl in Glendale, Ariz., also on New Year’s Eve.

The pairings for the four-team playoff were set Sunday when the CFP selection committee unveiled its final rankings of the season.

About 125 people associated with the Peach Bowl — volunteers, board members, staffers — gathered at a Dave & Buster’s restaurant in Marietta to watch and celebrate the playoff committee’s televised announcement.

“We’re ecstatic about the teams we’re getting,” Peach Bowl President and CEO Gary Stokan said. “To have the No. 1 team vs. the No. 4 team, to have the most significant college-football game ever played in this city, there are just so many things this game is going to bring to Atlanta.”

The game — the first national semifinal to be played in the Peach Bowl — will match the champions of the SEC and Pac-12. Alabama, the defending national champion, is 13-0, the only unbeaten team in the five power conferences. Washington is 12-1, losing only to USC.

Alabama has the nation’s No. 1 defense, allowing 11.8 points per game, while Washington has the No. 4 offense, scoring 44.5 points per game.

The Peach Bowl will be the final college football game played in the Georgia Dome, which will be replaced next year by the $1.5 billion Mercedes-Benz Stadium under construction next door.

Alabama was assigned by the playoff committee to the semifinal closest to its campus as a perk of getting the No. 1 seed.

“We’re excited to come back to Atlanta,” Alabama coach Nick Saban said Sunday. “Great host city, great place to be.”

In 10 games at the Georgia Dome under Saban since 2008, Alabama is 9-1 — 5-1 in SEC Championship games and 4-0 in Chick-fil-A Kickoff games. It has won eight in a row in the Dome, including Saturday’s 54-16 rout of Florida in the SEC title game.

Washington hasn’t played in the Georgia Dome previously.

“Everybody knows about Alabama … how dominant they are,” Washington coach Chris Petersen said Sunday in Seattle. “Fortunately, the Seahawks are here in town. Maybe they’ll scrimmage us to get us ready.”

The playoff’s other semifinal, in the Fiesta Bowl, pits ACC champion Clemson (12-1) against an Ohio State team (11-1) that failed to reach the Big Ten Championship game.

In one inconsequential change in the top four of its final rankings, the selection committee flip-flopped Ohio State and Clemson, dropping the Buckeyes from No. 2 to No. 3 and lifting the Tigers from No. 3 to No. 2 after their win over Virginia Tech in the ACC Championship game.

The Peach Bowl will start at 3 p.m. on New Year’s Eve, followed by the Fiesta Bowl at 7 p.m.

The semifinal winners will meet in the national championship game Jan. 9 in Tampa, Fla.

Alabama was established as an early 14-point favorite over Washington and Ohio State is favored by three points over Clemson, according to oddsmaker RJ Bell of Pregame.com.

The selection committee’s final rankings stirred debate about the value of winning conference championships and of scheduling difficult non-conference opponents.

Ohio State became the first team to reach the three-year-old playoff without winning its conference championship, while Penn State, which beat Wisconsin in the Big Ten title game and earlier defeated Ohio State, didn’t make the playoff.

Washington made the playoff despite an ultra-weak non-conference schedule, while Big 12 champion Oklahoma was left out because of losses in tough non-conference games against Houston and Ohio State.

In the end, the committee placed in the playoff the only four power-conference teams with fewer than two losses.

Three teams ranked just outside the top four — No. 5 Penn State, No. 6 Michigan and No. 7 Oklahoma — have two losses apiece.

“I know it was a really hard decision for the selection committee. There are such really good, deserving teams out there,” Washington’s Petersen said. “We’re just honored and proud and excited to be part of this whole thing. We don’t take any of this for granted.”

The committee moved Penn State up from No. 7 to No. 5 after the Nittany Lions’ victory in the Big Ten title game. Although missing out on the playoff, Penn State will play in the Rose Bowl against USC.

In comparing Washington to Penn State for the final spot in the playoff, the committee considered the Nittany Lions’ big wins over Ohio State and Wisconsin but also weighed their losses to Pittsburgh and Michigan, the latter by 39 points.

“It was a close call between Washington and Penn State,” committee chairman Kirby Hocutt said. “After considerable conversation about whether Washington or Penn State was better, the committee concluded that Washington is the better team.

“I think our discussions and our decision would have been much easier if Washington would have had a stronger strength of schedule.”

Washington recently took a step to bolster a future non-conference schedule, agreeing to play Auburn in the Chick-fil-A Kickoff game in Mercedes-Benz Stadium at the start of the 2018 season. When scheduling that game, the Huskies didn’t know they would be making a cross-country trip to Atlanta much sooner.

“Adapting to the time change is going to be the least of our problems playing Alabama,” Petersen said.