This was a match that had everyone gripped, and it was a sign of things to come when a stretch of five points saw four mini-breaks. The pair continued to exchange mini-breaks with the score at 8-8, and Opelka saved a set point on the return. Amazingly, the point always went in the way of the server until Opelka ended this seemingly endless battle with a brilliant backhand pass to win the match.
"I lost track," Opelka said afterwards as he described the tie-break.
"At one point it was 21-all. That's something I've never seen before, but if it was going to happen, it certainly would have been in this match."
"It just shows how clutch he is," when referring to Isner.
"I had some house money being up a set. He didn't, and he hit some unbelievable spots on his serve down match point."
The victory for Opelka sees him move to his fourth tour-level final. It was a stellar display from the 24-year-old, who fired 39 aces during the game – a two-sets record since this was data was first gathered in 1991.
This incredible contest did not see a break point, with both men winning more than 85 per cent of their first-serve points.
Opelka now turns his attention to Jenson Brooksby in the final, as the latter saved four match points to overcome Marcos Giron, 6-4, 6-7(4), 7-6(5).
Jenson Brooksby nie przestraszył się Djokovicia
Image credit: Getty Images
Brooksby heads into the contest looking to secure his first ATP Tour Title in what will be only the second meeting between the pair.
The 21-year-old recorded a straight sets win over Opelka in a round of 32 match at a ATP Tour event in Antwerp last year.
Opelka is clearly wary of the threat which Brooksby possesses and said before a potential match-up: “He is one of my favourite players to watch, probably my least favourite player to play."
Brooksby heads in the final ranked 54th, while Opelka is ranked 23rd.
Stream the 2022 Beijing Olympic Games live and on demand on discovery+