But number one seed Murray showed the resilience that carried him to the top of the tennis rankings last November as he inflicted a heartbreaking loss on Kohlschreiber.
The Briton finally bagged the second set tiebreak on his eighth set point to level the match. The ATP said no men's tour-level match has featured a tiebreak with more than 38 points since 1991 - six have finished 20-18.
"I've never played a tiebreak like that ever, not in juniors, nothing has been close to that," Murray, who is contesting his first tournament since losing in the fourth round of the Australian Open in January, told reporters.
"I'll probably never play another one like that again. I've been playing on the tour for 11, 12 years now and nothing, nothing's been close to that."
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With no end to the tiebreak in sight, Murray, Kohlschreiber and the umpire were left confused as the players forgot to change ends when they were locked at 15-15. Tennis rules state players have to change ends every six points during a tiebreak.
"I realised at 16-16 (that we had not changed ends), the umpire said he forgot and the (scoring) machine didn't recognise it, I do not know if the machines are made to go that high, it doesn't happen every often," added Murray.
The tiebreak left Kohlschreiber running on empty in the third set and Murray needed just another 30 minutes to secure a meeting with seventh-seeded Frenchman Lucas Pouille, who beat Federer's Russian conqueror Evgeny Donskoy 6-4 5-7 7-6(2).
"I could have easily lost tonight, but the way I played when I was behind will give me a lot of confidence after what was a tough start to the year," said Murray. "I want to keep that going now. It was a special match to win because of how it went."
The other semi-final will feature Fernando Verdasco of Spain and Dutchman Robin Haase, both unseeded.
(Reporting by Pritha Sarkar, editing by John Stonestreet)
