the court, the Melbourne crowd erupted in a loud "Tiafoe, Tiafoe" chant.
Khachanov struck a crosscourt forehand wide to go down set point at 6-1.
Facing a seemingly inevitable fifth set, Khachanov raised the level of his game to hit two aces out wide as well as a crosscourt forehand winner.
Meanwhile Tiafoe struck three forehand errors as Khachanov held a matchpoint at 6-7.
The two players traded several following points until Khachanov held a second matchpoint at 8-9 after he hit a crosscourt backhand passing shot winner.
Tiafoe then struck a stunning crosscourt forehand dropshot winner to reach 9 all.
However on the following point, the American netted a crosscourt forehand to trail 9-10 and face a third matchpoint.
Khachanov struck a powerful serve out wide to Tiafoe's backhand to begin the final point of the match.
The American netted a final crosscourt backhand return to end the match after three hours and thirty-two minutes of play.
Although Tiafoe appeared to have entertained the crowd more with his outgoing personality and his mix of power and finesse, it was Khachanov who finished the match with the stronger serve and more consistent game which proved to be the keys of the tiebreaker.
For the day Khachanov hit 52 winners including 20 aces to 27 unforced errors.
Tiafoe struck 65 winners but ended the high level match with a costly 53 unforced errors.