ATP roundup: Nick Kyrgios (knee) withdraws from Atlanta Open

Wimbledon finalist Nick Kyrgios withdrew from the Atlanta Open before his scheduled first-round singles match on Tuesday.

Kyrgios, who won an opening-round doubles match with fellow Australian Thanasi Kokkinakis on Monday, sustained a knee injury that caused him to exit the singles draw.

Kyrgios went on the court Tuesday to address the Atlanta crowd, saying, "I just want to say that I'm extremely shattered that I'm not able to compete tonight. I've won this tournament (in 2016) and, you know, I'm playing some of the best tennis of my career.

"All I wanted to do was come out there and give you guys a show and obviously see what I'm capable of, but I'm unable to give out my best performance today."

France's Adrian Mannarino, a lucky loser from qualifying, took Kyrgios' spot and beat German qualifier Peter Gojowczyk 6-3, 7-6 (7).

No. 5 seed Tommy Paul and No. 6 seed Jenson Brooksby were among the several Americans who won their respective first-round matches.

Paul breezed past countryman and wild card Jack Sock 6-1, 6-1, while Brooksby eliminated France's Benoit Paire 6-3, 6-1. In another all-American match, Mackenzie McDonald outlasted Denis Kudla 6-2, 7-6 (8) after Kudla fumbled away a 5-1 lead in the second-set tiebreak.

Other winners were Americans Ben Shelton and Andres Martin, Ilya Ivashka of Belarus and James Duckworth of Australia.

Croatia Open Umag

No. 5 seed Alex Molcan of Slovakia was a 6-2, 7-6 (2) winner over Croatian Duje Ajdukovic in first-round action in Umag, Croatia.

No. 8 seed Lorenzo Musetti, fresh off winning the Hamburg European Open title last week, joined Molcan in the second round. The Italian advanced with a 6-2, 3-6, 6-1 victory over Aljaz Bedene of Slovenia.

French qualifier Corentin Moutet upset sixth seed