MADRID (AP) Juan Martin del Potro marked his clay-season debut with a 6-3, 6-3 win over Damir Dzumhur in the second round of the Madrid Open on Tuesday.
It was the 22nd triumph this season for the sixth-ranked Del Potro, who has the most victories on the ATP Tour in 2018.
''I was playing well out there,'' said Del Potro, who won back-to-back titles in Acapulco and Indian Wells earlier this year.
Del Potro's next match is against Dusan Lajovic, who defeated Richard Gasquet 7-6 (1), 7-6 (1).
In the women's event, top-ranked Simona Halep reached the third round by beating Elise Mertens 6-0, 6-3.
Halep converted her fifth match point to win her 14th straight match in Madrid and stay on track for a third consecutive title in the Spanish capital.
''I knew she was coming with a lot of confidence,'' Halep said. ''I had to start very strong and aggressive, which I did. After I played a few games I felt really good.''
The 16th-ranked Mertens has played well this year but struggled from the start at the Magic Box and ended up with 31 unforced errors and five double faults.
She was coming off an impressive 13-match winning streak, with titles in Morocco, Switzerland and Tasmania. She also reached the Australian Open semifinals, losing to eventual champion Caroline Wozniacki.
Halep next faces Kristyna Pliskova, who defeated Sara Sorribes Tormo 7-5, 6-2.
''She's serving pretty strong,'' said Halep, who beat Pliskova in Madrid in 2017. ''I have to just watch a little bit how I played last year and to do it again. I believe I can win the match but I always expect a tough one.''
Crowd favorite Garbine Muguruza, ranked third, fought back to defeat Donna Vekic 2-6, 6-4, 6-1 while Petra Kvitova knocked out Monica Puig 6-3, 7-6 (8) to record her seventh straight win.
In the men's event, Fernando Verdasco defeated Paolo Lorenzi 7-5, 6-4 to claim his 500th win, while Robin Haase beat Hyeon Chung 6-2, 6-0 for his 200th victory.
''Getting the 500th victory is an unbelievable number that I never even thought about,'' said Verdasco, who became the 45th man in ATP Tour history to reach the milestone. ''I'm super-emotional and super-happy.''
Kyle Edmund defeated Daniil Medvedev 6-4, 6-0 to set up a second-round encounter with Novak Djokovic, while Milos Raonic upset third seed Grigor Dimitrov 7-5, 3-6, 6-3 to reach the third round.
Denis Shapovalov hit 38 winners to oust Benoit Paire 7-6 (5), 4-6, 6-4 in the second round and 11th seed Roberto Bautista Agut beat Jared Donaldson 6-7 (3), 6-4, 6-4 in the first round.
Borna Coric upset ninth seed Pablo Carreno Busta 6-4, 6-2 in another first-round match, while Pablo Cuevas rallied to defeat 12th seed Jack Sock 6-7 (5), 6-4, 6-0.
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