Then the heavens opened and, as the rain swept across Melbourne Park, Safin raised his arms in celebration, knowing he had been given a lifeline.
"Thank God, it started to rain," the Russian said. "I had no chance to win if it doesn't rain...I need that break and God gave it to me."
When play resumed 45 minutes later, with the stadium roof closed and the air conditioning cranked up, the 2000 US Open champion reeled off 11 of the next 13 games to clinch a 6-7, 7-6, 3-6, 6-0, 6-2 victory.
"I just changed the game completely, I played great, I served well, I did the right things," Safin, the 2000 US Open champion, said. "I don't know what he had in his mind...I didn't give him any chance after the break."
Nothing could separate the two players in the first two sets as they won a tiebreak each. But Safin was looking weary as early as the third game of the second set.
The volatile Russian exploded at the end of that game which gave Haas a break, hurling his racket into the ground and smashing it to pieces.
Struggling with the heat, the ninth seed called the trainer, saying he was finding it hard to move and had "no reaction" in his legs.
The former world number one took an injury time-out, was given aspirin, vitamin C and had both thighs massaged before returning to the court.
Haas comfortably won the third set 6-3 as Safin continued to wilt. The Russian won his opening service game before rain swept the stadium and play was suspended by referee Peter Bellenger.
Safin returned after the rain delay looking fresh and fit on centre court and quickly took control of the match. His new composure slipped at 1-1 in the deciding set, however, when he was called for a foot-fault on a second serve to give Haas a break point.
"I cannot believe! I cannot believe!" Safin bellowed at umpire Mike Morrissey.
He asked Morrissey to keep a close eye on his feet while serving, saying: "Please, look close, this it the first time in my life."
He steadied himself and held for 2-1 before grabbing the vital break for 3-1 and stretching into a 4-1 lead. He served for 5-2 and clinched his stunning victory after a demoralised Haas double-faulted.