(Photo credit: Mike Frey-Imagn Images)

Top-seeded Taylor Fritz fought off a stiff test from U.S. countryman Marcos Giron to earn a 6-4, 5-7, 7-6 (1) win in the first round of the Nexo Dallas Open on Tuesday.

Fritz posted a 21-9 edge in aces and won 81% of his first-serve points. However, he managed to break Giron's serve in just two of his 10 opportunities.

Second-seeded Ben Shelton of the United States bested Canada's Gabriel Diallo 6-4, 6-4, but two other seeded players fell. Great Britain's Jack Pinnington Jones trounced fourth-seeded Flavio Cobolli of Italy 6-2, 6-2, and Croatia's Marin Cilic edged sixth-seeded Learner Tien of the U.S. 7-5, 7-6 (4).

It was the 600th career ATP Tour win for Cilic, 37, who joined Serbia's Novak Djokovic (1,168) as the only active players to reach that milestone. He also passed Goran Ivanisevic's total of 599 wins to top the all-time list among Croatians.

Other winners were Aleksandar Kovacevic and Alex Michelsen of the United States and Miomir Kecmanovic of Serbia.

In the last match of the night, defending champion Denis Shapovalov of Canada, the seventh seed, was set to oppose Rafael Jodar of Spain.

ABN Amro Open

Serbia's Hamad Medjedovic, a lucky loser from qualifying, took advantage of his late entry into the event at Rotterdam, Netherlands, and defeated Belgium's Zizou Bergs 7-6 (5), 7-6 (5) in the first round.

Medjedovic, who entered the draw when Hungary's Fabian Marozsan withdrew, trailed 5-2 in the first set and fought off a set point in the next game before capturing the tiebreaker. The players exchanged service breaks in the 11th and 12th games of the second set, and Medjedovic again came through in a tiebreaker.

Top-seeded Alex de Minaur of Australia downed France's Arthur Fils 7-6 (3), 6-2, and the Netherlands' Tallon Griekspoor beat France's Giovanni Mpetshi Perricard 6-4, 6-4. France's Quentin Halys and Germany's Jan-Lennard Struff also advanced.

IEB+ Argentina Open

Argentina's Juan Manuel Cerundolo pulled off a first-round upset in his home land, defeating fifth-seeded Daniel Altmaier of Germany 6-2, 6-2 in Buenos Aires.

Altmaier struggled with his serve, putting just 69% of his first serves in play and winning only 35% of his second serves. He also committed 30 unforced errors to Cerundolo's nine.

Sixth-seeded Camilo Ugo Carabelli won an all-Argentine matchup against Francisco Comesana 6-4, 7-6 (3), and eighth-seeded Matteo Berrettini of Italy ousted Argentina's Federico Coria 7-5, 7-5. Also moving on were the Czech Republic's Tomas Barrios Vera, Argentina's Roman Andres Burruchaga and Peru's Ignacio Buse.

--Field Level Media