(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.  QUESTIONS:

Q1:
1. Who participated in the US Open?
2. What's the name of a US Open player?
3. Who is someone that was a participant in the US Open?
Q2:
1. Who did Rafael Nadal best?
2. Who was bested by Rafael Nadal?
3. Which player did Rafael Nadal beat?
Q3:
1. What were the scores of Nadal and Djokovic's matches?
2. What did Nadal and Djokovic score in the matches against each other?
3. When Nadal and Djokovic faced each other, how many points did each get?
Q4:
1. What were Rafael Nadal's scores in the Davis Cup?
2. What scores did Rafael Nadal have in the Davis Cup?
3. How many points did Rafael Nadal get in the Davis Cup?
Q5:
1. What took place in 2011?
2. What was an event from 2011?
3. What did 2011 mark for Rafael Nadal?
Q6:
1. What ruined Rafael Nadal's season?
2. Why was Rafael Nadal's season ruined?
3. What put a huge damper on Rafael Nadal's season?
Q7:
1. What kind of injury did Rafael Nadal sustain?
2. What was the nature of Rafael Nadal's injury?
3. How was Rafael Nadal hurt?
Q8:
1. Who was the victor against Ukraine?
2. Who came out on top against Ukraine?
3. Who was the player that bested Ukraine?
Q9:
1. Did Fernando Verdasco lose after beating Ukraine?
2. After defeating Ukraine, did Fernando Verdasco lose?
3. Was Fernando Verdasco bested after defeating Ukraine?
Q10:
1. What will Rafael Nadal undergo?
2. What is Rafael Nadal going to partake in?
3. What is Rafael Nadal set to do?
