Evans, from Carmarthen, was at least guaranteed a bronze by progressing to the last four of the competition, but his brave effort to reach the final ended when the towel came in after one minute of round four.
Yet the 22-year-old was ahead going into the third round until Cuba's six-time gold medallist turned on the power, although the Welshman was more exhausted than hurt at the end.
Evans received a public warning for dropping his head too low in the first round and was decked by a body shot in round two. That punch looked low, but in the third Evans had to take a standing count.
Savon has taken the gold in every championships since those staged in Reno in 1986, defending his title successfully in Moscow, Sydney, Tampere, Berlin and Budapest - in addition to winning Olympic golds in Barcelona and Atlanta.
Those statistics summed up the size of the task facing Evans. He at least became Britain's first ever World Championships medallist, although Ireland won bronzes in 1982, 1989, 1993 and 1997.
All of Britain and Ireland's other competitors, including an eight-strong England team, went out of the competition before the medal stage.