Henman was hoping to surpass last year's run to the quarter-finals

The Briton raced through the first seven games with ease but lost the next seven as Greul levelled at one set all.

And a nervous Henman then let a 4-2 lead slip in the decider as world number 130 Greul fought back.

With a tie-break looming the German broke Henman for the fifth time to seal the win, and he goes on to face Andy Roddick in round four.

His level went from nonexistent to playing some pretty good stuff in the space of a game Tim Henman

Greul beat Paradorn Srichaphan and Dominik Hrbaty in his opening two matches in Miami, but he showed none of that form in the early stages against Henman.

A rash of errors and double faults saw him lose the first set in 18 minutes, and it was not until the eighth game that the German got off the mark - something he celebrated by raising his arms in mock triumph.

It seemed to revitalise Greul, while Henman - who beat Marat Safin and Lleyton Hewitt in the previous rounds - lost concentration.

The second set disappeared almost as quickly as the first, and Henman was into a final set.

Henman should have cleaned him up in the second, instead he started playing negative tennis From TW Have your say on Five Live

Greul saved three break points in his first service game, but two games later another double fault gave Henman the seemingly decisive break.

But with victory in sight, Henman's nerve faltered.

Errors from the Briton contributed as Greul levelled at 4-4, and four games later the German took full advantage by sealing the match with a forehand winner.

"No doubt the most bizarre I've ever played," is how Henman described the match afterwards. "I'm shocked, really.

"His level went from nonexistent to playing some pretty good stuff in the space of a game.

We're going to have to do some scouting Andy Roddick

"After having beaten Safin and Hewitt and then having a match like this - it certainly doesn't sit well with me."

Greul, however, was delighted, particularly with the way he came back from such a poor start.

"At the beginning, I was a little bit nervous on the big Stadium Court and didn't play that good," he said.

"But then in the second set I got in the game, played some good balls and got a little bit confident and it was a close match in the third set.

"You know, I'm very happy that I won it."

His next opponent Roddick admitted that Greul is a mystery as he has never seen him in action for a full match.

"We're going to have to do some scouting," Roddick said.

"I was able to catch a little of the match against Tim, but I'm going to try to ask around."