Nadal and Djokovic faced each other the semi-finals of the Madrid Open last week which the former won in straight sets on the way to the title.
The 14-time men's singles Grand Slam champion, who beat Sock 6-3, 6-4 on Thursday (18 May), will face his opponent from the Madrid Open final Dominic Thiem in the last eight.
The four-time champion edged past local player Roberto Bautista Agut in straight sets (6-4, 6-4) in his R16 match yesterday to continue his quest to hit peak form after parting ways with his coaching team last month.
Djokovic, beaten in the final by Britain's Andy Murray a year ago, will now face Juan Martin del Potro in the quarters after the unseeded Argentinian's 7-6 (7/4), 6-3 win over Japanese seventh seed Kei Nishikori. "I can keep serving better". Isner did not lose his serve at all against Wawrinka, and Isner recorded the only service break of the match in the seventh game of the second set.
The biggest casualty of the day was US Open champion Wawrinka, American Isner surprising the world number three with a 7-6 (7-1) 6-4 victory.
Serbian tennis star Novak Djokovic on Monday said he remains as motivated as ever to reclaim his old position at top of the Association of Tennis Professionals (ATP) rankings, although he has not played his best match this year.
"I think I can play a little bit more aggressive than what I did tonight. I am very proud and humbled".
Arsenal keep their Champions League hopes alive
The Gunners play their second last Premier league game of the season tonight against already relegated Sunderland . Arsenal remained fifth in the standings, a point behind Liverpool and three adrift of Manchester City.