Image source, Getty Images

Tsonga is persisting with his forays to the net - with mixed results. He plants a backhand volley long before Murray unfurls a perfect lob to take it to 30-all. Tsonga picks a bad time to serve a double fault, giving Murray a break point, but Murray can't pull off a forehand pass. Two huge serves later and Tsonga has a two-game lead.

Nick Bollettieri
American tennis coach on BBC Radio 5 live sports extra

"The concern I have for Andy Murray - not only in this match, but to win another grand slam - is that he needs to get more zip on his second serve."

Murray is undergoing one of those worrying blips that he seemed to eliminate under Ivan Lendl's watch. He slips to 15-30 down on his serve, but with the spectre of a double break looming, he finds his poise to force two errors from Tsonga and take the game.

Tsonga, sweat glistening on his forearms, is in full flow, whipping forehands into the corners and prowling around the court with intent. When Murray nets a simple backhand, the break is consolidated.

Image source, AP

Tsonga shows his prowess at the net to open the door to a service break at 30-30. Murray hammers home a rare smash, but is pegged back to deuce by Tsonga. A piledriver of a backhand earns the Frenchman a break point and Murray loses his focus fatally at the key moment when he tamely surrenders the game by netting a dreadful drop shot. Oh Andy. Just when we thought you'd turned a corner, you go and reverse straight into the gate post.

This is a strange one. At 40-0, Tsonga appears to be distracted by some sweat dripping into his eye and completely misses the ball. The Frenchman claims he pulled out but the replay tells a different story and the umpire calls second serve. Murray nets the return anyway and Tsonga has his hold.

Tsonga makes an early statement of intent in the second set with blistering winners off both flanks to take it to 30-30. Murray responds with greater depth and puts away a winner from halfway through the court. A strong serve puts Tsonga on the back foot and the Frenchman concedes the game with a forehand that misses the side line.

One of the most eye-catching aspects of the first set was the players' neon trainers.

But they're not to everyone's taste - actor and comedian Will Ferrell gave Andy Murray's fashion sense a playful put-down when the pair met at the tournament this week.

Jeff Tarango
Former professional tennis player on BBC Radio 5 live sports extra

"Wow. I loved the fist-pump right into the Tsonga face. Murray's been looking sharp ever since that cramping incident (against Robin Haase). What I loved about that cramping incident was that he didn't ask for a trainer. I loved that attitude."

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Murray steps things up when it matters. Some clever changes of pace induce errors from Tsonga and give Murray two set points. Tsonga saves the first with a brute of a backhand, but Murray chips and charges on the second, putting away the set with a brilliant backhand volleyed winner. Sensational tennis from the British number one.

Jeff Tarango
Former professional tennis player on BBC Radio 5 live sports extra

"Andy is in control of his service game. He has to keep it segregated in his mind, between the frustration of returning and the confidence of serving."

No let-up from Murray. Tsonga can hardly lay a racquet on the Scot's serve and will now have to serve to stay in this first set.

There's a bit of a pattern emerging. The deeper a rally goes, the more likely Tsonga is to win the point. The Frenchman, dressed all in black, opens up a 40-15 but nets a backhand to give Muzza hope. A huge forehand from the Frenchman, however, seals the deal and takes it to 5-5.

At 0-30 down, Tsonga decides enough is enough and drills an unreturnable shot to Murray's backhand. But a neat overhead gives Murray a 40-15 lead and the Scot wraps up the game with a blast down the middle that Tsonga can only nick to first slip.

Image source, AFP

It's a straight-sets win for top seed Novak Djokovic. The Serb has seen off Philipp Kohlschreiber 6-1 7-5 6-4 in two hours and three minutes to reach the quarter-finals. His next opponent? It'll either be Andy Murray or Jo-Wilfried Tsonga.

Anything you can do? Tsonga cramps up Murray with a body serve and holds to love. Meanwhile, we now know the man the winner of this match will be facing in the last eight...

Piers Newbery
BBC Sport at Flushing Meadows

"A collective sigh floats around the stadium as an unexpected gust of cool breeze drifts over the stands. The heat isn't worrying Murray so far, and he's a different player with the cavernous spaces of Ashe to explore, as opposed to the more confined Armstrong. With the breeze come the first few grey clouds looming into view."

Murray's serve has been almost flawless so far. An ace down the middle, his third of the match, puts him 4-3 in front.

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Kay Kas: , externalMurray will definitely win. Tsonga needs a proper breakthrough to be a champ.

ollie reynolds:, external Tsonga loses too many points easily, but if he is consistent he has a chance.

Murray has not failed to reach the quarter-finals of a Grand Slam since the US Open in 2010. Tsonga, the 2008 US Open runner-up, has not got past the fourth round at his last four.

But this is better from the Frenchman as he works Murray around the court and controls the game, holding serve to 15.