Montanes triumphed 6-2, 7-6 (7/5) to move to within one victory of repeating his 2009 title with the upset in a match which began with more than two hours of delay after downpours drenched the Estadio Nacionale.

The Spaniard, the ATP No. 34, will face off in the Sunday final against the winner from fifth seed Guillermo Garcia-Lopez and Portugal’s Frederico Gil.

Federer now goes into the Madrid Masters with a 2-2 record on clay and a title to defend in the Spanish capital.

Meanwhile, in Madrid  sixth-seeded Elena Dementieva cruised into the second round of the Madrid Open with a 6-0, 6-1 win against Aleksandra Wozniak of Canada on the clay of Caja Magica on Saturday.

Also, Alona Bondarenko of Ukraine came from a set down to beat Magdalena Rybarikova of Slovakia 2-6, 6-1, 6-4.

Vera Zvonareva of Russia beat Melanie Oudin of the United States 6-3, 6-4, and Austria’s Sybille Bammer defeated Kazakhstan’s Yaroslava Shvedova 6-4, 3-6, 6-3.

The tournament, which offers prize money of  $4.7 million for men and $4.5 million for women, runs through May 16.