Pat Cash
Former Wimbledon champion on BBC Radio 5 live

"You don't like to see anyone hurting this much. If it wasn't the final Nadal would have shaken hands and gone to the locker-room by now. You have to give him credit for carrying on."

Image source, Reuters

Nadal's head was bowed during the changeover and his body language suggests he's a broken man. Wawrinka coolly wraps up the set with an ace but will Nadal carry on? He receives more on-court treatment on that lower back...

The usually ebullient Aussie crowd have been stunned to silence by this unexpected turn of events. Once again Wawrinka has set points, two this time, although Nadal offers some resistance. He gingerly approaches the tape to slap away a winning volley and then watches Wawrinka go long. Deuce. Nadal directs a forehand into the tramlines for a third break point, but Wawrinka refuses to inflicted a killer blow on his wounded prey.

Image source, AP

Nadal was face down on the court during the changeover, with the physio massaging his lower back. Maybe the Spaniard is hoping the pain killers will take hold before throwing in the towel. He's currently as threatening as a three-legged giraffe as Wawrinka collects three points for a 40-0 lead. The Spaniard hauls his opponent to deuce, however, but Wawrinka throws in an ace - his ninth of the match - and seals the game with a backhand winner down the line. What has Nadal got left?

Nadal on the brink. He seems to fighting back the tears as well as back pain. There's no venom on the Spaniard's groundstrokes and he's serving at mobility-scooter pace. The world number one might call it a day. His shoulders are slumped, his head is bowed, he's spraying shots here, there and everywhere, and it's only a matter of time before the tears will start to flow. Two break points Wawrinka and he takes it with a backhand winner.

Piers Newbery
BBC Sport at Melbourne Park

"Nobody quite had the lack of grace to boo, but there were plenty of grumbles and moans when it was announced Nadal was heading off for a medical timeout. He certainly looked in real discomfort, grabbing at his back, during that last game and appeared to be limping a bit as he went down the tunnel. Not much fun for Wawrinka, sitting on his chair and hoping the mojo will still be with him when play resumes. OK, there is quite bit of booing when Nadal returns to the court. Quite feisty in here at the moment, and that's just the press seats."

Wawrinka opens with an ace. Kerpow! Then another. Kerboom! This game resembling the opening sequence to a Batman movie. Nadal offering no resistance. Three aces in total for Wawrinka who holds with ease.

Pat Cash
Former Wimbledon champion on BBC Radio 5 live

Image source, Reuters

"There's anger bubbling under the surface about these medical timeouts. Federer has said something in the past and Stan is sticking up for himself. The point is Carlos Ramos is engaging in a stand-up argument and he shouldn't. He should let the player vent. Stan is so angry at the moment - he's steaming."

Andrew Castle
Former British number one on BBC Two

"What Stan needs now is to maintain his composure. It can be really annoying when an opponent takes a timeout which might or might not be tactical."

A topless Nadal appears on court once again, but he seems to have overrun his allocated time. Boos from the spectators. Play will begin in a few seconds, though...

Tournament referee Wayne McEwan appears on court but there's no calming Wawrinka. The fired-up Swiss leaves his seat and is lunging on the baseline.

Image source, AFP

"It's between him and the physio at the moment," the umpire, Carlos Ramos, tells Wawrinka but the Swiss is adamant he should know. "You can fight about this or accept it," Wawrinka is told. Slow clapping rippling around the arena... Wawrinka seeing only red mist.

Nadal departs the scene and the umpire informs the spectators that Nadal is receiving a medical time out. Wawrinka gulps some water and remains seated. The Swiss is unhappy, however, and is exchanging a few angry words with the umpire, insisting that he should be told what is wrong with Nadal. What happened to patient confidentiality, Stan?

Pat Cash
Former Wimbledon champion on BBC Radio 5 live

"Wawrinka looks like the world number one playing the world number 60 in the first round. He doesn't over-think things. If the ball is short, he just whacks it. But there's something wrong with Nadal. He's lacking in power and there he's just stopped and doubled over. He's definitely being outplayed but he's not 100% sharp."

Image source, AFP

Wawrinka, oozing confidence, steps into the Nadal forehand and is a fraction wide with a backhand. The Spaniard, though, making uncharacteristic errors and he grabs his lower back after slapping a forehand into the tape. His face contorted in pain as he bends over and these are worrying times for the world number one.

At 40-30, Wawrinka pins him on the baseline and the top seed goes long. The usually indefatigable Nadal showing signs of weakness and will Wawrinka pounce? Not yet. Nadal comes through to take the game but he requires a medical time out.

Wawrinka collects three points with ease and the underdog has now won 12 points on the trot. Wawrinka received tips from Roger Federer prior to this match and although what was said between the pair has remained top secret, the 17-time Grand Slam champion must have given his compatriot some pearlers. Nadal attempts to battle back, taking the game to 40-30, but Wawrinka cruises to the net like a panther to punch a deep volley. The Swiss marches on.

Pat Cash
Former Wimbledon champion on BBC Radio 5 live

"The crucial thing now is that Wawrinka will start relaxing and will play even better. Nadal will have to step it up now. Nadal's shots have not hit the spot at all and he's being attacked. That was the perfect game from Wawrinka."

Nadal grunting as he unleashes one pulverising strike after another from the baseline. The Spaniard moves the Swiss this way and that... 20 shots... 21 shots... but momentum swings Wawrinka's way and a sublime clean winner from Wawrinka earns him the opening point. The Swiss then runs around onto his forehand to launch another unstoppable clean winner to go 0-30 up. Nadal then nets a forehand and looks towards his team. Three break points Wawrinka and this is not what the bookies had predicted.

Some fans are on their feet and rightly so because Wawrinka breaks Nadal with a wondrous backhand return.

This isn't the only big sporting clash in Australia today. England's cricketers are attempting to chase 218 to beat Australia in the final one-day international in Adelaide. England are 101-3 after 25 overs. Can they do it? Follow live text and Radio 5 live sports extra commentary on the BBC Sport website.

John Lloyd
Former British number one on BBC Two

Image source, Getty Images

"Wow. What a psychological boost for Wawrinka. He's only made one more unforced error than Nadal. While still going for the winners, he's keeping the errors low. But how did he get away with that final game?"