Nadal, a four-time Miami runner-up, leaves the Masters Series hardcourt event without a title again this year after his 11th appearance.
Verdasco, ranked 34th, defeated Nadal for the second time in a row after losing their first 13 meetings, although that most recent prior meeting came three years ago in Madrid.
“Obviously always beating a player like Rafa is one of the biggest victories that you can have in tennis,” Verdasco said. “It’s a huge victory and it’s always really nice to play in an almost packed stadium against one of the best players in history.”
Also advancing with victories Sunday were world number one Serena Williams and Britain’s Andy Murray.
Nadal saved a match point in the eighth game of the second set trailing 5-2, but Verdasco closed out the shocker a game later with a return winner.
The 14-time grand slam champion said after the defeat that his formerly untouchable game needs work and the mental side may now be his weak link.
“I need to fix again the nerves, the self control on court. It’s not a tough issue to fix. I’m going to keep trying,” Nadal said.
“I’m practicing with the right attitude, I think. I’m arriving in an important part of the season for me (clay). I didn’t want arrive to that part of the season with that loss of today, obviously, but that part of the season will arrive.”
Nadal, who will seek his sixth French Open title in a row in two months and bid for his 10th crown overall on the red clay of Roland Garros, says he will work on his control no matter how long it takes to recover his top form.
“I’ve been able to be under control, control my emotions during, let’s say, 90 percent of my matches, something that today is being tougher to be under self control,” Nadal said.
“But I’m going to fix it. I don’t know if in one week, in six months, or in one year, but I’m going to do it.”
Verdasco said he tried to remember how he played in the first set as he fought back after losing the second.
“I tried to play back again as I was the first set. I tried to keep calm and be aggressive, but of course at the same time you cannot be too aggressive,” Verdasco said. “It was very windy, and many times you need to adjust.”
– Murray takes 499th win –
Murray won his 499th career match, downing Colombian Santiago Giraldo 6-3, 6-4 to reach the fourth round.
The 27-year-old Scotsman, winner of the title in 2009 and 2013, would become the ninth active player to reach 500 victories if he wins his next match against South Africa’s Kevin Anderson, who eliminated Argentina’s Leonardo Mayer 6-4, 6-4.
“I obviously want to try and win more, and hopefully still have quite a few years ahead of me left to add to that number. It’s a lot of wins. It’s not easy these days to win that many matches, so that’s a good sign,” said Murray.
In women’s play, Williams crushed a teen less than half her age, defeating American Catherine Bellis 6-1, 6-1.
The 15-year-old challenger was no match for the 33-year-old Williams, a 19-time Grand Slam champion bidding for a record eighth trophy here.
Bellis, the junior world number one, found herself in a major test against the game’s current dominator in her first WTA appearance since the US Open.
World number one Williams is competing in Miami for the 15th time since debuting as a teenager herself in 1998, a year before Bellis was born.
– Serena win streak at 14 –
Williams will next face Russian Svetlana Kuznetsova, a winner over German 13th seed Angelique Kerber 6-3, 3-6, 6-3.
Aiming for a third consecutive Miami title, Williams stretched her win streak to 14 matches at Crandon Park. Her career Miami record now stands at 69-7.
Williams wrapped up the affair in 41 minutes with 15 winners and five breaks of the prodigy’s serve. Bellis committed 21 unforced errors.
“If you break down her age and her ability and how well I think she handled the moment and how well she played, I think it was good,” Williams said.
Third seed Simona Halep defeated Italy’s Camila Giorgi 6-4, 7-5 to continue the momentum she took from last week’s title at Indian Wells.