Juan Martin del Potro had little trouble moving on in his quest for another U.S. Open title.

The 18th-seeded Argentine beat countryman Diego Junqueira 6-2, 6-1, 7-5 Friday to advance to the third round. The 2009 champion was unable to defend his title last year because of wrist surgery.

While del Potro had little trouble, last year’s women’s runner-up, No. 2 Vera Zvonareva, needed two hours to defeat No. 30 Anabel Medina Garrigues, 6-4, 7-5.

Maria Sharapova had an afternoon match in Arthur Ashe Stadium, with defending champion Rafael Nadal, No. 4 Andy Murray and No. 21 Andy Roddick among those in action later.

The Zvonareva match in Ashe ended a long streak of lopsided affairs on the U.S. Open show court.