Top seed Nishikori rallied to beat Querrey 3-6, 6-3, 6-3 for his 16th consecutive Memphis victory over four years while Fritz, an 18-year-old American wildcard in only his third tour-level event, ousted Lithuania's Ricardas Berankis 2-6, 6-3, 6-4.

Fritz fired 17 aces in becoming the youngest American in an ATP final since a 17-year-old Michael Chang won at Wembley in 1989.

And he shattered the US mark for fewest tour-level events needed to reach a final, the 10 tournaments taken by Jimmy Connors and Andy Roddick.

After starting the week 1-2 in ATP play, 145th-ranked Fritz has won four matches and would crack the top 100 by taking the title.

"It feels incredible," Fritz said. "It's crazy what winning four tennis matches can achieve. I'm so happy."

Seventh-ranked Nishikori downed Querrey for the fourth meeting in a row, improving to 5-3 in their career rivalry by eliminating him in the semis as he did last year.

"It was a tough start for me," Nishikori said. "He was playing really good tennis, especially with his serve. He was hitting deep and flat and I was on defense all the time. I found my rhythm in the second set, was hitting balls deep and the tactics were working."

After splitting the first two sets with only one service break for each, Nishikori broke again for a 2-1 lead in the third set when Querrey netted a backhand.

Querrey had a break point in the eighth game, but Nishikori blasted a backhand winner to save it and start a run of six points in a row that took him to triple match point. Querrey rescued the first two break points but Nishikori hit a forehand winner for the triumph.

Fritz, last year's US Open junior champion, made his ATP debut last year at Nottingham, beating Carreno Busta before a second-round exit. He lost to compatriot Jack Sock in five sets in the first round of last month's Australian Open.

A double fault by 102nd-ranked Berankis handed Fritz a 2-1 edge in the last set. The European broke back for 4-4 with a service return winner only to double fault on break point again in the ninth game.

Fritz held to take the match in a wild final game that saw him squander four match points, then deny two break chances before Berankis netted a backhand to finally end matters after one hour and 40 minutes.

"It's incredible," Fritz said. "After the first set it wasn't looking too good. I was getting beaten every way possible. But I was able to turn it around and that makes it twice as good."