Isner upsets Cilic to reach Miami Open quarter

KEY BISCAYNE, Fla. (AP) — American John Isner upset second-seeded Marin Cilic of Croatia 7-6 (0), 6-3 on Tuesday to reach the Miami Open quarterfinals.

The 14th-seeded Isner, who reached the Miami Open semifinals in 2015, never faced a break point in the match. He made an impressive 73 percent of his first serves to take down Cilic.

"I was in a very good serving rhythm today," Isner said. "I felt that really from my opening serve, the whole match that I knew it was going to be a good serving day.

"When I serve like that, I'm certainly tough to beat," Isner added.

The key to Isner's victory in the match came when he won all seven points in the first-set tiebreaker.

"In the blink of an eye I was up 5-0 and I was able to win it 7-0, a very good tiebreaker, because prior to that the match was a bit choppy," Isner said. "The wind was of course tricky, and it was pretty ugly, but I played a very good tiebreaker."

The departure of Cilic, the 2014 U.S. Open champion and Australian Open finalist in January, leaves fourth-seeded Alexander Zverev of Germany as the highest seed remaining in the draw.

Top-seeded Roger Federer lost his opening match at the tournament, and third-seeded Grigor Dimitrov of Bulgaria lost in the third round.

Fifth-seeded Juan Martin del Potro, a definite crowd favorite in Latin-influenced South Florida, moved onto the quarterfinals with a 6-4, 6-2 win over 22nd-seeded Filip Krajinovic of Serbia.