HOUSTON (AP) — Fourth-seeded Steve Johnson beat top-seeded Jack Sock 4-6, 6-4, 6-3 on Saturday in an all-American semifinal in the U.S. Men's Clay Court Championship.

Johnson won his lone ATP Tour title last year on grass at Nottingham in England. He will face eighth-seeded Thomaz Bellucci of Brazil, a 5-7, 6-4, 6-2 winner over American Ernesto Escobedo.

"I just got lucky in the end," said the 27-year-old Johnson, a two-time national collegiate champion at the University of Southern California. "He missed some first serves and a couple forehands, which is abnormal for him, and I just took my chances and was able to get it. This is great, my first final on U.S. soil. It's fun to give myself a chance."

A week ago, Sock and Johnson were on the same side, coming up short together in a losing effort by the U.S. Davis Cup team in the quarterfinals against Australia.

"Whomever I'm playing, it's business," said Johnson, who had dropped four of his five previous ATP World Tour matches against Sock. "That's sports. You're going to play guys you're buddies with. You've got to put it aside and go about your business."

Sock won the 2015 event at Forest Oaks for the first of his three tour titles, and finished second last year. He's the highest-ranked U.S. player at No. 16.

"He played well at the end and deserved to win," Sock said. "He does what he does. He slices his return well and puts some in the corners."

Sock served almost flawlessly until the eighth game of the second set, when he double-faulted for the first time and faced double-break point. He extricated himself from that jam, but was finally broken in the 10th game, setting up another third set — his third in three days.

Sock broke back straight away, then held for 2-0 and 3-1 before Johnson charged, winning the final five games of the match. Sock save one match point with a crosscourt forehand winner, then ripped a forehand return down the line to reach break point himself before Johnson re-composed himself, leveling the game and putting Sock away with his 11th ace.

Bellucci has won four tour events, all on clay. Making his first appearance in the only ATP event played on clay in North America, he won his fourth three-set match in four days. It marked the first time in 27 years, going back to David Wheaton in 1990, that a player needed 12 sets to reach the final.

The 20-year-old Escobedo, a wild-card entry into the tournament, reached his first ATP-level semifinal after taking out John Isner, the 2013 champion and the No. 2 seed.

After breaking Bellucci in the 12th game of the first set to gain the upper hand, Escobedo struggled with his own serve the rest of the way. Before Houston, he'd never won an ATP match on clay. But getting to the semifinals lifted him to a provisional 72nd in the world.

Escobedo, having spent his formative tennis years on public hard courts in the West Covina area of Los Angeles, is the first Mexican-American to crack the top 200 since Pancho Gonzalez.

"I learned a lot of things this week, like that I can play on the clay," Escobedo said. "I like it a lot. It's fun. I'm enjoying myself on the court. So many players say it's not their best surface so they just tank. I feel like I belong in the ATP. I think my game is there. I just have to keep working. It's a long journey . . . I can't wait for the future."