Nadal, playing in his first tournament since his quarter-final loss to Russian Mikhail Youzhny in the U.S Open, could not threaten the awesome serving of Johansson, who won 6-4, 7-6 in front of an ecstatic home crowd.
In his first round match, Blake outclassed another Swede, Thomas Johansson, 6-3, 6-2.
The American world number eight, seeded second behind Nadal, broke Johansson's service early in both sets and never allowed the Swede to find his rhythm.
Throughout he displayed the powerful serving and solid ground strokes that have made him a contender for the season-ending Masters Cup in Shanghai.
"Once I got the first break, I gained a lot of confidence," said Blake, who is chasing his fifth ATP title this year after triumphing in Bangkok two weeks ago.
"You're never sure if your momentum is going to continue in a new city...it's a great feeling, I hope it continues throughout the week."
Blake, who defeated Thai Paradorn Srichaphan in last year's final, now faces Simon Greul in the second round. The German defeated Swede Ervin Eleskovic 6-4, 6-2.
"I was completely blown away," acknowledged Johansson, a winner in 2000 and 2004.
Former top-10 player Joachim Johansson, now ranked 690 in the world after a long shoulder injury lay-off, set the pace against Nadal by firing four consecutive aces in his first service game.
After breaking the Spaniard to 2-1, he comfortably held serve throughout the first set. He broke Nadal's opening service game in the second but later dropped serve himself, allowing the match into a tiebreak.
After grabbing a 3-0 lead, Johansson stayed on top to win the tiebreak 7-4 on a backhand return error by Nadal.
"I didn't play the match of my life, but I didn't play a bad match either," said Nadal. "Joachim was more aggressive. On the big points he was more aggressive, for sure.
"He has unbelievable potential, he has an incredible serve and an incredible forehand.
"He has the advantage over other players coming back from injuries, and that's his serve...He's one of the top five (servers), for sure."
Johansson fired 17 aces past the Mallorcan, who was rarely able to take charge of the rallies.
"I think this is my finest victory. I've won titles and I've gone far in grand slams, but considering how the last year has been, I rank this one the highest," said Johansson, who reached the U.S Open semis two years ago.