World number three Alexander Zverev beat teenager Alex De Minaur to defend his Washington Open title on Sunday.

Zverev beat the 19-year-old Australian 6-2 6-4 in the warm-up event for the US Open to claim a third ATP title this year after wins in Munich and Madrid.

“This match could be the final for the next 15 years so I hope you really enjoyed it,” said the German, 21.

Russian Svetlana Kuznetsova beat Croatia’s Donna Vekic 4-6 7-6 (9-7) 6-2 in the final of the women’s event.

It was an 18th career tour title for the 33-year-old two-time Grand Slam champion, who had slipped to 128th in the world heading to Washington.

Mihaela Buzarnescu won her first WTA title with a 6-1 6-0 victory against Greece’s Maria Sakkariat at the Silicon Valley Classic.

The 30-year-old wrapped up the final in just 73 minutes and has now broken into the world’s top 20.

Meanwhile, Fabio Fognini beat world number four Juan Martin del Potro 6-4 6-2 to win the Los Cabos Open.

Italian Fognini, 31, had beaten British number two Cameron Norrie to reach the final in Mexico.