Fourth-seeded Tommy Haas beat top-seeded Mardy Fish 6-3, 7-5 on Saturday to reach the Citi Open final.
Haas will face second-seeded Alexandr Dolgopolov, a 6-4, 6-4 winner over No. 8 Sam Querrey.
"He's always been a very dangerous player," Haas said about Dolgopolov. "You don't know what to expect, but a lot of firepower, a lot of crazy shots sometimes, but very, very dangerous."
In the women's final, unseeded Magdalena Rybarikova beat top-seeded Anastasia Pavlyuchenkova 6-1, 6-1 for her third career title and first of the year.
Haas committed no unforced errors in the first set.
"That's obviously something that doesn't happen often in my game, because I play very aggressively at times and miss a few balls here and there," Haas said. "But in order to beat people like Mardy Fish, you have to play at a very high level."
Haas ranked second in the world in 2002 before battling injuries. At 34, he said he's now "wiser" and calmer during matches.
"For a lot of the fans that like watching him play -- including myself -- he's certainly back to that standard," Fish said. "No disgrace losing to someone like that. I'm not happy with the result today, but happy with the week."
Haas is seeking his second tournament title of the year, and Dolgopolov is aiming for his first, which the Ukrainian said would be his biggest career victory. The two have never played each other on tour.
Haas, the German ranked 36th in the world, improved to 4-1 against Fish, and has won six of his last seven matches against top-15 players. Fish is ranked 15th.
Haas won 67 percent of his second-serve points to Fish's 46 percent.
Dolgopolov used his wide serve positioning to baffle Querrey, the winner last week in Los Angeles.
"He has an awkward-style game, and it makes it tough to play against," Querrey said.
After struggling to remember the English word `confidence' during an interview Friday, Rybarikova, from Slovakia, had plenty of it Saturday. She beat the tournament's top three seeded players en route to victory.
"It was just everything working for me this week," said Rybarikova, who brought her lucky charm, a stuffed duck, to her post-match news conference. "We are happy."