*

      Holder Alcaraz downs Humbert, Sinner fells Shelton

        *

      Gauff beaten by fellow American Navarro; Raducanu out

        *

      Injuries end Keys, Dimitrov campaigns

    By Shrivathsa Sridhar

       LONDON, July 7 (Reuters) - Defending champion Carlos

Alcaraz and world number one Jannik Sinner stayed on track for a

blockbuster Wimbledon showdown by reaching the quarter-finals,

while women's second seed Coco Gauff was sent tumbling out on a

soggy Sunday.

    French Open champion Alcaraz, who is looking to defend his

Wimbledon trophy and complete what is dubbed the "Channel Slam"

in reference to the English Channel that separates Britain and

France, battled past Metz-born Ugo Humbert 6-3 6-4 1-6 7-5.

    "I think I'm getting better and better every match that I'm

playing," said Alcaraz, who was happy to avoid another five-set

tussle after being taken the distance by Frances Tiafoe in the

previous round.

    "I'm feeling really comfortable on the court and hitting

good points, good shots."

    American 12th seed Tommy Paul set up a last-eight meeting

with the 21-year-old Spaniard after the Queen's Club champion

downed Roberto Bautista Agut 6-2 7-6(3) 6-2.

    Italian Sinner, who could face Alcaraz in the semi-finals in

a rematch of their Roland Garros meeting, was equally impressive

in his 6-2 6-4 7-6(9) win over 14th seed Ben Shelton.

    "I'm happy how I handled the situation," said Sinner, who

neutralised the feisty American's big serves to prevail.

    "It was obviously very, very tough to play against him, one

of the best servers we have on tour, very aggressive player.

    "I'm happy how I returned today. Yeah, I think that's for

sure one of the keys today."

    The 22-year-old will next meet fifth seed Daniil Medvedev,

who he defeated in January to win his maiden Grand Slam title at

the Australian Open.

    Russian Medvedev progressed when Bulgarian 10th seed Grigor

Dimitrov retired from their clash while trailing 5-3.

    Sinner's fellow Italian Jasmine Paolini also advanced thanks

to an injury to her opponent, as the teary Madison Keys withdrew

at 5-5 in the deciding set of their encounter with a suspected

groin problem.

    "I hope she recovers soon. We played a really good match. Of

course, it's not the easiest to end like this," Paolini said.

    "But I have to say that a part of me is happy to be here in

the quarter-final in Wimbledon."

    There was heartbreak for British fans as their last hope

Emma Raducanu was dumped out by 123rd-ranked qualifier Lulu Sun

who sealed a 6-2 5-7 6-2 win over the 2021 U.S. Open winner.

    Reigning Flushing Meadows champion Coco Gauff did not fare

any better as she was hammered 6-4 6-3 by fellow American and

19th seed Emma Navarro.

    Donna Vekic overcame several rain delays to get past Spain's

Paula Badosa 6-2 1-6 6-4 and book a clash with Sun.

(Reporting by Shrivathsa Sridhar in London

Editing by Christian Radnedge)

((Shrivathsa.Sridhar@thomsonreuters.com;))