Injured Djokovic Victorious

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.