No. 2 seed Taylor Fritz and fellow American and No. 3 seed Ben Shelton won in straight sets Wednesday to reach the quarterfinals of the BOSS Open in Stuttgart, Germany.

Fritz struck 12 aces and recorded the only service break of the match in a 6-3, 7-6 (6) win against Quentin Halys of France. Up next is Hungarian Marton Fucsovics, a 7-6 (4), 6-3 winner over Frenchman Arthur Rinderknech.

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Shelton saved four break points in the second set before closing out a 7-6 (4), 7-5 win over France's Pierre-Hugues Herbert. His opponent in the final eight will be eighth-seeded Czech Jiri Lehecka, who posted a 6-4, 7-5 win against Germany's Jan-Lennard Struff.

Libema Open

Fifth-seeded Hubert Hurkacz of Poland overcame a mid-match back injury to defeat Spain's Roberto Bautista Agut 7-6 (2), 6-4 in 's-Hertogenbosch, the Netherlands.

Hurkacz fired 16 aces and won 90 percent of the points on his first serve but needed a medical timeout during the second set. His second-round opponent will be Estonian qualifier and World No. 195 Mark Lajal, who registered a 6-2, 6-4 upset of Serbia's Laslo Djere.

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No. 3 seed Karen Khachanov of Russia outlasted Mackenzie McDonald 6-3, 5-7, 7-6 (4). Canada's Gabriel Diallo saved two match points in a 4-6, 6-1, 7-5 upset of No. 6 Jordan Thompson of Australia. Britain's Daniel Evans and France's Adrian Mannarino also advanced.