By Martyn Herman
LONDON (Reuters) - Rafael Nadal again offered a chink of light to an opponent on his way to the last 16 at a gloomy Wimbledon on Saturday but another former champion Maria Sharapova was taking no chances under the Centre Court roof.
For the third match in a row Spaniard Nadal found himself a set in arrears against an inspired adversary, this time in the form of Kazakhstan's 63rd-ranked Mikhail Kukushkin, before switching on the after-burners to romp home 6-7 (4) 6-1 6-1 6-1.
With play suspended on every court apart from Centre because of persistent rain, Sharapova then won 11 games in a row after a sluggish start against American Alison Riske, roaring into the second week with a 6-3 6-0 victory.
Among those watching Nadal and Sharapova continue their title assaults was former England soccer captain David Beckham, one of numerous high-profile sportsmen and women occupying the Royal Box.
Nadal's matches have followed a familiar pattern.
Against Slovakian Martin Klizan and Czech Lukas Rosol he was overpowered in the opening set, so it was no surprise to witness him slip behind against Kukushkin, one of three men in the third round with a female coach - in his case his wife.
Despite losing the tiebreak there was never the same sense of danger as in the previous round against the hard-hitting Rosol who knocked out the Spaniard two years ago.
Once 14-times grand slam champion Nadal broke early in the second set Kukushkin's belief drained away and there was only ever going to be one outcome.
"When I played the first set I said that maybe the roof here in Wimbledon is not good for me," said the sun-loving Nadal whose 64 career titles include only two indoors.
"I don't like to be in closed places only with lights but I think I played a great match. It didn't affect me a lot," he told reporters.
The rain eventually relented at around 1730 local time but it was too late to prevent the schedule being shredded with Swiss Stanislas Wawrinka's clash with Denis Istomin and Feliciano Lopez's duel with John Isner being canceled.
With Wimbledon the only grand slam not to play on middle Sunday, tournament officials will have some re-organising to do ahead of Monday which is traditionally last-16 day in the men's and women's singles.
Sharapova, seeking a rare French Open-Wimbledon double 10 years after her previous triumph at the All England Club, cranked up the volume on Centre Court - her loud shrieking echoing off the translucent roof.
Once she found her range she looked unstoppable and Riske, the daughter of a retired U.S. Secret Service agent, offered little resistance.
"I am happy to be in the second week after missing out last year," said the Russian who suffered a shock second-round defeat in 2013.
(Editing by Tony Jimenez)