Roger Federer expressed surprise on Monday that long-time rival Rafael Nadal has not played tennis in nearly two months, with the Swiss world number one concerned about the state of the Spaniard as the Cincinnati Masters begins.

“I was going to write him and check on him, because I can’t believe he’s been out that long,” Federer said of the former number one, who last played in a huge Wimbledon second round loss to Czech Lukas Rosol on June 28.

Since then, the third-ranked king of clay has gone to ground as he tries to heal chronic tendinitis in his knees, which threaten to rule out his entire summer hard-court campaign, including the US Open.

Nadal withdrew from the London Olympics with regret and then pulled out of both of this month’s Masters 1000 tune-ups for the US Open starting on August 27 by missing the Toronto and Cincinnati events.

“I thought the Olympics, okay, that’s fine. That’s a personal choice,” said Federer.

“I thought for sure we would see him in Toronto, but now he missed Toronto and Cincinnati. It’s very surprising, because it was nothing that we heard of prior to the injury. He played so well on clay, and then actually seemed fine at Wimbledon. He had more (recovery) time by losing earlier at Wimbledon.”

Federer called it a “big surprise, these two pullouts. I’m sad for him. I hope he’ll be back for the Open.”

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