Alexander Zverev roared back to beat Pablo Carreno Busta 3-6, 2-6, 6-3, 6-4, 6-4 and reach the US Open final after a comprehensive comeback.
In what was a low-quality match littered with unforced errors, Zverev somehow managed to haul himself back into it to reach his first Grand Slam final from two sets down.
Carreno Busta looked in complete control after he took the second set 6-2 with the German utterly devoid of confidence on both his serve and groundstrokes.
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But the fifth seed battled his way back into the match as the Spaniard grew weary and sustained an apparent back injury and eventually came through to clinch his place in Sunday's showpiece.
The turnaround was quite remarkable given that Zverev committed an astonishing 36 errors through the first two sets, but in the end he took the win with his second match point.
"I was actually looking at the scoreboard when I was down two sets to love and I was like 'I can't believe it, I am playing in the semi-final where I am supposed to be the favourite and I am down two sets to love," said Zverev.
"I knew that I had to come up with better tennis and I knew that I had to be more stable ... but I am through to my first Grand Slam final and that's all that matters."
The 23-year-old will attempt on Sunday to become the first German Grand Slam champion since Boris Becker triumphed at the Australian Open in 1996 as he takes on Dominic Thiem, who overcame Daniil Medvedev.