* "Goodbye beloved badminton," Yu Yang says
* Putin to visit Olympics, judo diplomacy with Cameron
* Britain hoping for gold rush after Wiggins, rowers
* Phelps, Lochte slug it out for one last time in the evening
By Ossian Shine
LONDON, Aug 2 (Reuters) - The Olympic play-to-lose badminton fiasco took a fresh twist when China's Yu Yang quit the sport in anguish, and later on Thursday black belt President Vladimir Putin and British leader David Cameron will grapple over Moscow's position on Syria in a day of judo diplomacy.
Cameron welcomed Putin, honorary president of the International Judo Federation, to Downing Street and will urge the former KGB spy to take a tougher line on the civil conflict in Syria, Russia's firmest foothold in the Middle East.
The pair are expected to visit the Olympic arena to watch the judo together and focus on what Putin critics see as an intensifying Kremlin campaign to silence dissent, against a backdrop of fair play and Olympic ideals.
There has been precious little evidence of either at the badminton arena so far, where eight women from China, South Korea and Indonesia were kicked out of the Games for playing to lose group games in order to secure easier knockout berths.
China's state news agency Xinhua pulled no punches, blaming the debacle on head coach Li Yongbo's "evil strategy".
"Athletes should not get a paddling when it is head coach Li Yongbo's evil strategy that is the major reason," Xinhua said in a commentary on the affair.
That public support was not enough to appease Chinese player Yu Yang who quit the sport after national officials told their Olympic team leaders and disgraced players to make a public apology for throwing matches.
"This is my last competition. Goodbye Badminton World Federation, goodbye my beloved badminton," Yu wrote on her Tencent microblog. "We ... only chose to use the rules to abandon the match.
"You have heartlessly shattered our dreams. It's that simple, not complicated at all. But this is unforgivable," said Yu, who with Wang Xiaoli, was top-seeded in the women's doubles.
The shameful shuttlecock debacle cast a shadow over Thursday's sporting action, which will see Americans Michael Phelps and Ryan Lochte clash for the final time in the pool, with Phelps, once again, vying to become the first male swimmer to win the same individual event at three Olympics.
The United States could do with a Phelps or Lochte gold as they aim to keep China in their sights in the medal table. The Chinese top the standings with 17 gold among their haul of 30 medals on Day Six of competition.
The United States sits second with 12 gold from 29, with South Korea third on six and the French team with five.
A collective sigh of relief was heaved over the length and breadth of Britain on Wednesday when they finally struck gold after four days of failure in archery, shooting, judo, handball and canoeing.
Helen Glover and Heather Stanning ended the drought when, like ancient alchemists, they converted guts and heart into glittering gold in rowing's women's pairs at Eton Dorney -- a performance that sent Twitter into meltdown.
Glover only started to row four years ago and Stanning, an army captain who may be sent to Afghanistan next year, two years before that.
Tour de France winner Bradley Wiggins, a blunt-speaking Londoner, then cruised to victory in the men's cycling time trial. "Vodka and tonic helps," responded the man whose ginger sideburns have become the must-have fashion look, when asked if his achievements had yet sunk in.
Britain's newspapers went into overdrove, with tabloid headlines blaring "Golden wonder", "Gold rush" and "GOOOOOOOOOOOLD!"
The spotlight has been on match officials following the badminton embarrassment, and incidents at boxing table tennis, but the focus will be squarely on sporting prowess later on Day Six when swimmers Phelps and Lochte slug it in the evening.
The two Americans teamed up on Tuesday in the squad that crushed the rest of the field in the 4x200 metres freestyle relay to give Phelps his 19th Olympic medal, and the title of most decorated Olympian.
The duo now go head to head in the 200 individual medley for one last tantalising clash before Phelps retires. Lochte drew first blood in London by winning the 400 version on Saturday, pushing Phelps into fourth place.
"We love racing against each other," Phelps said. "Neither one of us likes to lose. I like to say we bring out the best in one another."
Olympic track cycling action gets under way with Britain's Victoria Pendleton, a nine-times world champion, renewing her battle with Australia's Anna Meares and hoping to end her career on a high on home soil.
With Germany holding the world titles in both team sprints, the hosts will be hard pressed to repeat their showing in Beijing where they won seven of 10 possible golds.
But they will draw inspiration from Wiggins who followed victory in last month's Tour de France by running away with the time trial, 42 seconds ahead of Germany's Tony Martin.