American tennis has been surging this season, with a title run at the inaugural United Cup followed by a strong showing at the Australian Open from the nation's men. Taylor Fritz was part of that victorious United Cup team, but he was up against a countryman in Jack Sock to begin his Dallas Open campaign on Thursday evening.

The top seed lived up to his status as the ATP Tour's No. 1 American with a 7-6(5), 6-4 victory, winning a rematch of his most recent meeting with Sock one year ago at the same event. With that result, Fritz moved up one place to No. 7 in the Pepperstone ATP Live Rankings, setting himself up for a new career high on Monday.

"I thought I played pretty well," Fritz said of his first match since a second-round Australian Open exit. "He served well and when I got chances on his serve he played the points well, so it was pretty tight. I wasn't really able to find that break, but I played well, I protected my serve well, and I'm pretty happy with the match."

The World No. 8 converted only one of his seven break chances, but he did not face a break point on his own delivery behind 10 aces and a 91 per cent win rate on first serve.

Both players were aggressive on the indoor hard court, with a combined 60 winners and 34 net approaches between the two. In the rallies, Fritz found the Sock backhand as often as he could, with Sock content to slice his replies off that wing while he patiently waited for an opportunity to unleash his big forehand.

Over the course of one hour, 36 minutes, Fritz did just enough to advance in straight sets and set up an all-American quarter-final against seventh seed Marcos Giron, who closed the evening's play with a 6-4, 6-3 win against Germany's Oscar Otte.

Fifth seed John Isner also advanced on Thursday with a 6-3, 7-6(1) win against Daniel Altmaier. He will meet Emilio Gomez in Friday's quarters after the Ecuadorian's 2-6, 7-6(4), 6-4 upset of fourth seed Miomir Kecmanovic. Gomez, whose father is former World No. 4 Andres Gomez, is through to his first ATP Tour quarter-final.

In other action, eighth seed Adrian Mannarino was a 6-2, 7-6(3) winner against Jordan Thompson. The Frenchman will meet China's Wu Yibing for a place in the last four. The other Dallas quarter-final will see Wednesday winners Frances Tiafoe and J.J. Wolf square off in an all-American matchup.