UPDATE 3-Tennis-Thrilling Nadal rally sets up final with Federer

* Nadal saves three match points in win over Djokovic

* Federer coasts to 6-3 6-4 victory over Del Potro

(adds Federer result, Nadal quotes)

By Iain Rogers

MADRID, May 16 (Reuters) - Claycourt maestro Rafael Nadal shrugged off a knee problem and saved three match points to beat Novak Djokovic 3-6 7-6 7-6 in a dramatic semi-final at the Madrid Open on Saturday.

The world number one was a whisker away from his fifth defeat in 154 matches on his favourite surface since the beginning of 2005 but rallied superbly to set up a final against Roger Federer.

At almost four hours three minutes it was the longest three-set match in a Masters Series event and it thrilled the Spaniard's partisan home crowd at the new Magic Box stadium.

Federer's clash with Argentine Juan Martin Del Potro failed to touch the same heights later, the second seed coasting to a 6-3 6-4 victory.