Welcome to the live coverage of the US Open quarter-final clash between Novak Djokovic and Jo-Wilfried Tsonga. Hopefully we'll be up and running soon

Novak Djokovic will now play Gael Monfils in the semi-final having played only two of a possible five full matches so far in the tournament. Bad news for Andy Murray fans...

Djokovic 6-3 6-2 Tsonga: Tsonga's knee injury was clearly too much to bear, and he certainly would have had to have upped his game to progress any further. A sad way to go for the ninth seed.

And unbelievably, Djokovic has another opponent retire on him!

Djokovic 6-3 6-2 Tsonga: Djokovic is undeterred by the medical time out and serves out the set in just moments. He signs off with an ace - there will be no tea and sympathy from the world no.1.

In fairness he might have to retire from the match if his knee is as bad as his face just said it was...

Some strapping is being taped around the offending knee but it looked quite bad for a minute, there. He's on his feet again, nonetheless.

Tsonga is having his knee looked at by a member of his team and looks visibly uncomfortable, wincing at times. He's going to get some treatment now.

Djokovic 6-3 5-2 Tsonga: Djokovic challenges the first point and it's his - Tsonga's shot was just out. Djokovic looks like he could break again here but a furious rally ensues with Tsonga stepping up. He hits the net again and Djokovic has done it and will serve for the second set now.

Bit harsh...

Djokovic 6-3 4-2 Tsonga: Djokovic looks frustrated as he hits the ball out to hand Tsonga a point, but it's an untroubled serve by and large. Ben Stiller's in the crowd and he's texting at the moment, apparently.

Djokovic 6-3 3-2 Tsonga: Tsonga holds his serve as the game goes to deuce and Djokovic's return meets the net to consolidate Tsonga's advantage. They both look very focused.

Djokovic 6-3 2-1 Tsonga: These guys look pretty evenly matched but Tsonga's game is more inconsistent. and these are the points Tsonga will regret most as he finds the net again. Its another early break by the Djoker.

Djokovic 6-3 1-1 Tsonga: Djokovic is close to being broken by Tsonga, but he pull sit back. He's incredibly agile on the court and he always seems to find something when he's under real pressure.

Djokovic 6 -3 Tsonga: Djokovic somehow manages to break Tsonga again (his serve is hitting 131mph now, incidentally) and holds on in there to consolidate with by holding his own serve.

Djokovic 4-3 Tsonga: And the Frenchman breaks right back. Though both have been assisted by sloppy errors.

Djokovic 4-2 Tsonga: Tsonga's serve is strong, to the power of 124mph in fact, but it's not enough to stop Djokovic who has perhaps got the measure of his opponent, breaking in almost straight points.

Djokovic 3-2 Tsonga: Tsonga puts some pressure on Djokovic now and for a brief moment, it feels as if he could even break him, but it's not to be, just yet.

Djokovic 2-2 Tsonga: Tsonga's serve is looking good recording 120mph already. He's not giving Djokovic much to play with.

Djokovic 1-1 Tsonga: A steady start for Djokovic and a steadier one for Tsonga, though Djokovic occasionally makes an audacious display of athleticism, spinning to backhand the ball from behind his body, just so we know he can.

Tsonga and Djokovic are on their way to the court now. This will only be Djokovic's third full game of the tournament - assuming Tsonga doesn't retire early like two of his competitors have done already.