Nicolas Colsaerts and Graeme McDowell fought off stunning comebacks from Gonzalo Fernandez-Castaño and Bo Van Pelt respectively to set up a rematch of last year’s final at the Volvo World Match Play Championship.
The Ryder Cup teammates will meet in the last eight at Thracian Cliffs Golf & Beach Resort, but only after both being given a real scare in the last 16.
Defending champion Colsaerts won the first five holes – Fernandez-Castaño aiding his cause with four bogeys in that run.
The Belgian was still five up with five to play, but incredibly got taken to the final green before holding his nerve for a two up victory.
“I should have ended this game about an hour, an hour and a half ago,” said a relieved Colsaerts. “I have a putt to win the game on 13, and there's a par five, and I made a bit of a mess of it. Thank God it's over.
“It's never over. I finished the same way Gonzalo started - he handed me a couple of holes too easily early on, and I did the same on the last stretch. If you go through a bad 20, 30 minutes, you can make moves one way or another.”
Last year’s beaten finalist McDowell had looked in imperious form during the group stages, and when he turned four up on Bo Van Pelt – who qualified without a win after halving both round-robin fixtures – the Northern Irishman looked odds on to proceed.
The American had other ideas, however, and won the 13th, 15th and 16th with birdies to take the contest down the 18th.
Former US Open Champion McDowell had missed a six footer for the win at the 17th, but a par at the last proved enough for a one up victory.
“You can never count a player of Bo Van Pelt's standard out of any match,” said McDowell.
“I got off to a fast start again - every day I've played those first eight holes beautifully.
“I kind of lost my rhythm a little bit, Bo found his eye with the putter coming in and holed some nice putts and really kept me honest.
“It’s nice to get the job done. A repeat of last year's final [this afternoon].
“He's beaten me twice, the last two years running in this tournament, s you could say I might owe him one.
“We'll see, he's a great player, looking forward to getting out there. I'm obviously relieved now just to get past Bo Van Pelt and go and prepare myself for this afternoon.”
Meanwhile Brett Rumford's bid to join Sir Nick Faldo and Seve Ballesteros in the record books came to an end at the hands of Branden Grace.
After back-to-back wins at the Ballantine's Championship and Volvo China Open two weeks ago, Rumford was looking to become only the third man in European Tour history to win three consecutive events.
However, South Africa's Grace reproduced the form that saw him beat Colsaerts in the group stages to seal a 4 and 3 win.
Grace was five up at the turn thanks to five birdies and some errors from his opponent, but had to survive a superb fightback from Rumford, who birdied four holes in a row from the tenth.
With Grace, a winner of five titles worldwide last year, only able to match one of those the gap was suddenly down to two, but Grace responded with birdies on the 14th and 15th to seal the win.
The 34 year old, who finished 18th on his Masters debut last month, will face Chris Wood in this afternoon's quarter-finals after the Englishman beat South Africa's Richard Sterne 5 and 3.
Italy's Francesco Molinari also advanced to the last eight with a comprehensive 6 and 4 win over Sweden's Carl Pettersson, the Ryder Cup star facing Thomas Aiken after he beat Shane Lowry at the first extra hole.
Lowry had come through a play-off in the group stages but this time found a fairway bunker and water down the first extra hole to gift Aiken the win.
Scott Jamieson holed from 30 feet across the 18th green to seal victory over Felipe Aguilar and was left to face Thongchai Jaidee after he overcame Peter Hanson in a marathon match that went to the 21st hole.
After a quick break for lunch, Colsaerts and McDowell were back on the course and seemingly none the worse for their hard-fought wins.
Both players birdied the second and Colsaerts also birdied the third to go one up, with the other three quarter-finals also close in the early stages.
Three birdies in succession from the fifth for Grace were only enough to get back on level terms with Wood, while Molinari and Aiken were all square after four and Jamieson one up on Jaidee after a birdie at the first.