(Photo credit: Susan Mullane-Imagn Images)

Second-seeded Ben Shelton and defending champion Flavio Cobolli, the fourth seed, both were upset victims on Tuesday at the Hamburg Open in Germany.

Home favorite Daniel Altmaier stunned World No. 6 Shelton 4-6, 7-6 (4), 6-4 in two hours, 51 minutes to advance to the quarterfinals. Altmaier, who entered the tournament with a 4-13 record this season and ranked No. 65, came back after Shelton had a chance to serve out the match up 5-4 in the second set.

Peruvian qualifier Ignacio Buse downed Italy's Cobolli 6-2, 7-5 in one hour, 31 minutes. Buse recorded more winners (15-13) and never faced a break point.

Top seed Felix Auger-Aliassime of Canada defeated the Czech Republic's Vit Kopriva 7-5, 6-1 in the first round. Other winners were fifth-seeded Karen Kachanov of Russia, seventh-seeded Luciano Darderi of Italy, France's Ugo Humbert and American lucky loser Aleksandar Kovacevic. A second-round match between sixth-seeded Tommy Paul and Argentina's Tomas Martin Etcheverry was suspended due to darkness. Etcheverry won the first set 7-6 (5), and Paul took the second by the same score.

Geneva Open

Two days after losing to World No. 1 Jannik Sinner in the Italian Open final, sixth-seeded Casper Ruud of Norway got back to winning with a 6-3, 7-5 victory over Jenson Brooksby in the first round in Switzerland.

Ruud, ranked No. 17 in the world, converted five of 10 break points against Brooksby, who had more winners (28-21) and more unforced errors (22-12).

Eighth-seeded Jaume Munar of Spain dispatched American qualifier Nishesh Basavareddy 6-0, 6-3; Belgium's Raphael Collignon beat France's Adrian Mannarino 6-3, 7-6 (5); Australia's Alexei Popyrin outlasted French qualifier Clement Tabur 7-6 (2), 6-7 (5), 6-4; and Serbia's Laslo Djere downed Australia's James Duckworth 6-4, 3-6, 6-3.

--Field Level Media