Red-hot Ian Poulter defeated Sergio Garcia in Tucson - but went to bed not knowing his final opponent at the World Golf Championships-Accenture Match Play Championship.
Fellow Englishman Paul Casey, last year's runner-up, will resume a marathon match with Colombian Camilo Villegas at 7.10am local time.
After Casey missed a nine foot par putt for victory on the final green they went five extra holes at Dove Mountain before darkness forced them off.
It looked all over for sixth seed Casey - not taken beyond the 14th hole en route to the last four - at the final hole of the day, but Villegas missed a par putt from under three feet in the gathering gloom.
That came three hours after Poulter had defeated Garcia by a huge 7 and 6 margin on another fantastic day for The European Tour contingent.
After making the final Poulter breathed a sigh of relief that he had not jinxed himself at his hotel.
Because of loud music on Friday evening he asked for a change of room and was taken to one ending in 13.
"I was questioning whether to go back, but stayed - and I'm not moving now, am I?" he said with a smile.
All four semi-finalists had to cope with monsoon-like conditions for the best part of an hour early in their matches.
"It was very, very difficult over the first three or four holes," said Poulter. "It was nice to get out there and get up early on Sergio. Then it was just nice that rain did back off so we could actually play some sensible golf. It certainly wasn't enjoyable. The golf would have been terrible to watch. Guys making double bogeys everywhere and that's not really any fun.
"Once that cleared up then I hit a lot of good golf shots and a lot of birdies and made it difficult on Sergio.
He added: "It would mean an awful to win. I think it would certainly put me in a position for The Ryder Cup. To win on this side of the pond would be another particular box in the boxes that are still unticked, so it would be good."
Garcia and Casey both found themselves one down in their respective matches after opening with double bogey sixes in the rain, wind and cold.
At the 208 yard third Garcia had a semi-shank into the lake, and Casey also found himself two down after an even bigger mistake.
The sixth seed's tee shot was so badly mishit that it travelled little more than 100 yards. He was even short of the water, but then pitched into it and, like Garcia, lost the hole to a bogey four.
Play had been held up for nearly 15 minutes just before, but on the resumption Poulter took the next three holes as well and after losing the seventh birdied the next three and won after Garcia missed the green on the short 12th.
Casey was two down after three, but battled back to lead by one with one to play. He might yet regret his missed putt on the last, but then saved himself with a superb chip-and-putt birdie over a bunker at the fourth extra hole after his opponent had played a spectacular 50 yard bunker shot to within inches of the cup.
In the morning quarter-finals Casey made Open Championship winner Stewart Cink his four successive 5 and 4 victim - and left America without a semi-finalist for the first time in the 12-year history of the event.
"I have no idea what's happening," said Casey. "I know how tough Stewart is. He has a great record in match play.
"I never thought we would be standing here (by the 14th green) talking. I thought it would go all the way. I'm very happy, but shocked."
Cink, second and then third in the event the last two years, jokingly showed his conqueror where the 15th tee was. He has not needed to go there yet.
"I saw a great display," said Cink, whose only success came when Casey drove wildly into the desert on the long 11th and had to take a penalty drop.
Poulter came back from one down on four separate occasions to defeat Thai Thongchai Jaidee with a seven foot par putt on the final green.
It might have been an all-English semi, but Oliver Wilson lost 4 and 3 to Garcia, while Villegas completed a clean sweep of European Tour Members when he defeated an out-of-sorts Retief Goosen by the same margin.
Poulter, who went out in the semi-finals to David Toms in San Diego five years ago, said: "It was difficult out there - the wind started to blow around that back nine and it started to get very, very cold."
