Montreal’s Gabriel Diallo was ousted in the third round of the Citi Open hardcourt tennis tournament Thursday with a 6-3, 6-2 loss the fourth seed Ben Shelton of the United States.

Shelton was nearly unbeatable on serve, firing 16 aces to Diallo’s five and winning a whopping 86 per cent of total service points.

The American did not face break point while breaking Diallo three times on four chances.

Diallo, seeded 15th in Washington, entered the tournament with a career-high world ranking of No. 35.

He will next play at the National Bank Open in Toronto, where he is seeded 30th and will have a first-round bye.

Later Thursday, Leylah Fernandez of Laval, Que., faced top seed Jessica Pegula of the United States in a women’s third-round match.