Rafael Nadal's record of 13 French Open titles will never be broken, says Britain's Andy Murray.

The nearest to the Spaniard's total in the Open era is Bjorn Borg, French Open winner six times between 1974 and 1981.

"It's an amazing achievement," Murray said. "I don't think it'll be repeated, I don't think anyone will be close."

Federer hailed Nadal's victory as "one of sport's greatest achievements" and Murray echoed the Swiss legend - citing how the Spaniard's record compares with 14-time Grand Slam champion Pete Sampras, one of the greats of tennis.

"He is one short of winning the same amount of Grand Slams as Sampras - just at one tournament," said the Scot. "It's incredible."

Murray, 33, suffered a first-round defeat by Stan Wawrinka in Paris this year as he works his way back from hip surgery.

He plays Spain's Fernando Verdasco at a tournament in Cologne on Tuesday and said: "I was told it would be an 18-month process for my body to get used to it. It changes the way your pelvis moves and your body needs to adjust.

"Hopefully with a few matches this autumn and some good training, next year will be a good one."