Naomi Osaka has withdrawn from this week’s Italian Open with an Achilles injury.

The four-time grand slam champion sustained the problem at the Madrid Open last week and struggled during a second-round loss to Sara Sorribes Tormo.

Osaka said in a statement: “Unfortunately I’m going to have to withdraw from Rome as the injury which I picked up last week in Madrid hasn’t healed yet. It’s an Achilles injury so I need to be careful, especially in advance of Roland Garros.”

Meanwhile, veteran Stan Wawrinka claimed his first victory since last year’s Australian Open over 14th seed Reilly Opelka.

Wawrinka, 37, was off the tour for just over a year following surgery on his foot, making his comeback at the end of March.

Opelka, a semi-finalist in Rome last year, looked to be in control at a set and a break up but Wawrinka battled his way back into the match and turned things around impressively against the giant American to win 3-6 7-5 6-2.