For the first time since 2009, an American man will play in a Grand Slam final.

Frances Tiafoe guaranteed the drought will end when he beat ninth-seeded Grigor Dimitrov on Tuesday night inside Arthur Ashe Stadium, hours after fellow American Taylor Fritz ousted fourth-seeded Alexander Zverev.

The 20th-seeded Tiafoe and 12th-seeded Fritz will play in the first All-American men’s semifinal in a Grand Slam since Andre Agassi beat Robby Ginepri in Flushing in 2005.

“Yeah, me, Taylor [Fritz], Tommy [Paul], Reilly [Opelka], we’ve spoken about it for years, this is the group, this is the group. You know, we openly speak about it. I think we all been knocking on the door…. It’s only a matter of time,” Tiafoe said. “You put yourself in positions, it’s only a matter of time. And the game is open. It’s not like it once was where you make quarterfinals, you play Rafa [Nadal], and you’re looking at flights. I mean, that’s just the reality. Now it’s just totally different, you know. And no one’s unbeatable.”

Friday night’s winner will be the first American man in a slam final since 2009, when Andy Roddick lost the Wimbledon final to Rodger Federer.

In what started as a tight match, Tiafoe defeated Dimitrov in four sets — 6-3, 6-7, 6-3, 4-1 — across 3 hours, 4 minutes before the Bulgarian was forced to retire with a leg injury.

Up 4-3 in the third set, Dimitrov noticeably slowed down, occasionally grabbing his left hamstring and was walking very gingerly between points.

He struggled to put up a fight and two unforced errors gave Tiafoe the set.

Dimitrov went for treatment after the third set, but pulled the plug five games into the final set.

“Not that much to say right now,” Dimitrov said after the match. “I mean, first of all, you know, congrats to Frances. Fought very hard. Played good tennis. Really good tennis, actually. Yeah, it’s just a disappointing moment for me.”

With the win, Tiafoe reached his second U.S. Open semifinal in three years.

“It’s different on Ashe, man. It’s different. Obviously you have to learn from those. You know, I mean, couple of those I thought I actually should have won,” Tiafoe said of Fritz. “He’s tough, man. He’s a tough player. He plays great from both sides, has a great serve, he’s moving much better now. It’s going to be tough. It’s going to be a big one for both of us, playing for a final.”

It was a night for the history books, one filled with cheers in celebration of finally having home-court favorites deep in the tournament — with much of that due to early exits from Carlos Alcaraz and Novak Djokovic — hoping to end the 21-year American grand slam title drought.

Roddick was the last to hoist a major trophy, winning the U.S. Open in 2003.

There was no shortage of cheers behind Tiafoe with the occasional “NY loves Tiafoe” hats among the crowd and there were frequent chants of “Let’s go Tiafoe!”

The pair met four previous times before Tuesday with Dimitrov leading the series 3-1. In Tiafoe’s single win, he got off to a hot start.

He did again Tuesday night.

The first set saw both Tiafoe and Dimitrov win their service games to start, but Tiafoe had the first break in the fifth game with a backhand volley winner.

Tiafoe nearly broke Dimitrov again in the seventh game, but failed to do so, but got the double break to close out the set.

Nevertheless, the momentum shifted in the second set.

Tiafoe got up to a 4-1 lead, but it quickly went away as Dimitrov found his groove, winning 91 percent of his first serves and tallying four aces.

He broke the American’s serve for the first time in a deuce battle in the seventh game.

After defending another break opportunity, Tiafoe failed to break Dimitrov to force a tiebreak at 6-all.

After two double-faults, the seven-point tiebreaker was in Tiafoe’s favor, only trailing 6-5, and the crowd went wild as it turned to his serve.

Yet, anticlimactically, the American double-faulted to give up the second set — the pressure clearly being felt by both players.

Tiafoe only nailed 43 percent of his first serves in the set.

Nevertheless, Tiafoe managed to go on a run in the third set much to the Arthur Ashe crowd’s delight and carried it through until the final set ended early.