(CNN) -- They played in the U.S. Open final Monday but both Rafael Nadal and Novak Djokovic were back in action for their countries Friday.

They both won, too, overcoming fatigue, jet lag and a change of surface.

Nadal, who beat Djokovic in New York to claim his 13th grand slam title, prevailed 6-0 6-0 6-4 over Sergiy Stakhovsky -- Roger Federer's conqueror at Wimbledon -- on his favored clay.

He boosted his Davis Cup record in singles to a near invincible 21-1, with his lone reverse coming in his first outing against Jiri Novak in 2004.

Nadal hadn't played in the competition since 2011, opting to skip proceedings in 2012 even before his season was ruined by a knee injury.

"Today is another victory after a long year and every victory is important," Nadal told the Davis Cup website.

With Fernando Verdasco also winning his match in Madrid against Ukraine, it means Spain is on the verge of retaining its spot in next year's world group following an upset loss to Canada in February.

Nadal is scheduled for the potential doubles clincher Saturday alongside good pal Marc Lopez. If he does take to the court, it would be his first doubles tussle in the Davis Cup in seven years.

"To play with a good friend like Marc will be a special feeling, first time in the Davis Cup," said Nadal.

Canada kept on progressing in the Davis Cup and encountered Djokovic's Serbia in its maiden semifinal Friday.

But Djokovic was too strong in the opener versus big-serving Vasek Pospisil, cruising 6-2 6-0 6-4 on clay in Belgrade.

Answer the following questions:
1. Who played in the US open
2. Who did Nadal beat?
3. what were the scores?
4. What scores did he have in the Davis Cup?
5. What happened in 2011?
6. Why was his season ruined?
7. What kind of injury?
8. Who won his match against Ukraine?
9. Did they lose afterwards?
10. What is Nadal is scheduled for?
1. Rafael Nadal
2. Djokovic
3. 6-0 6-0 6-4
4. 21-1
5. it was the last time he played in the competition
6. an injury.
7. a knee injury.
8. Fernando Verdasco
9. unknown
10. the potential doubles clincher