Rafael Nadal will miss Spain’s Davis Cup final against Argentina because of a knee injury.

The top-ranked Nadal said Monday he was still struggling with tendinitis in his right knee following a week of treatment.

“These are very difficult moments, but I have done all that I could to be ready for the final,” he said. “It was a huge objective, and I’m used to playing with pain, but this is a distinct, new, pain that I couldn’t control.”

Nadal’s absence deals a big blow to Spain’s bid for a third Davis Cup title since 2000. Spain captain Emilio Sanchez Vicario has until Tuesday to name his team.

Spain plays Argentina on indoor hard court at Mar del Plata from Nov. 21-23.

Nadal was a key player when Spain beat the United States 4-1 in the semifinals, winning both his singles matches.

Sanchez Vicario most likely will replace Nadal with Tommy Robredo or clay-court specialist Nicolas Almagro. David Ferrer, Feliciano Lopez and Fernando Verdasco are expected to be back on the team.

Nadal this year won a fourth straight French Open and his first Wimbledon title. He withdrew from the Paris Masters last month with an injury to the same knee after losing the first set of his quarterfinal against Nikolai Davydenko. He then pulled out of this week’s season-ending Masters Cup in Shanghai, China.

Nadal also won the Olympic gold medal in a year when he supplanted Roger Federer at No. 1.