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By Matt Cronin
BOISE, Idaho April 7 (Reuters) - Novak Djokovic overcame an early injury to his ankle and lifted Serbia to the Davis Cup semi-finals with a gritty 7-5 6-7 6-1 6-0 victory over American Sam Querrey on Sunday.
"It's very strong emotion when you play for your country. I guess that's the biggest reason why I kept playing," Djokovic told reporters after securing Serbia an unassailable 3-1 lead.
"It meant a lot to me personally and the whole team and the nation, and we are very glad to be in semi-finals again."
Serbia will play Canada in the semi-finals in September.
The world number one Djokovic took a bad spill in the third game of the first set, and had to be helped off the court to have his right ankle treated.
But after wrapping his ankle in a medical timeout, Djokovic returned to the court where his movement was not seriously hampered.
The Serbian's big-match experience came to the fore when he broke the towering American to 6-5 in the first set and sealed it with a series of high bouncing kick serves to his opponent's weaker backhand side.
Querrey rallied in the second set, dictating play with his big serve and forehand to take it to a tiebreak.
Djokovic suffered a rare lapse to surrender the set, pushing a back-court volley wide and missing another forehand to hand Querrey the tiebreak 7-4.
The Serbian said that the anti-inflammatory medication he took for his ankle injury began to kick in from there, while Querrey's service speed slowed due to a strained right pectoral muscle.
The American double-faulted to fall 2-0 behind in the third set, and Djokovic sped away, dropping only a single game for the rest of the match as he yanked Querrey around and gleefully attacked his second serves.
"He broke me early and got some momentum and then just kind of started swinging more freely," Querrey said. "He started to become a great frontrunner at that point. Made it tougher on me."
After sealing the match with a backhand winner, Djokovic hugged his team mates and took a bow to the fans that had travelled from Europe to support them.
Novak is such a complete tennis player," said U.S. captain Jim Courier. "We've seen him grow over the years not only game-wise but mentally.
"He's got a lot of that ... to draw from the matches when he's been pushed to the brink. There are not a lot of holes to pick on Novak."
Djokovic will fly home to Monte Carlo on Monday to have a scan on his swollen ankle and may be in doubt to play the Masters tournament there next week.
(Editing by Ian Ransom)