ROME — When John Isner received an invitation to play a charity exhibition match in Seattle in late April with Roger Federer, his initial reaction was to double-check the date.

“First, I said, ‘Roger’s doing an event in Seattle then?’” Isner recalled, surprised that Federer, the Swiss star, planned to be in the Pacific Northwest in the middle of the European clay season.

Federer, 35, had already decided to skip clay Masters events in Monte Carlo, Madrid and Rome, and made his absence from clay events complete last week, announcing he would withdraw from the French Open, which will begin Sunday.

“I need to recognize that scheduling will be the key to my longevity moving forward,” said Federer, who has won three hardcourt events this year, including the Australian Open.