With a costly double bogey immediately after hitting the lead, Marc Leishman wrote another chapter in his Torrey Pines heartache.
The 33-year-old Victorian - one of nine golfers who held at least a share of the lead during a dramatic final round at the Farmers Insurance Open - was blown away by Jon Rahm's back nine of six-under-par.
Chasing his first victory on the US PGA Tour, the 22-year-old Spaniard shot a brilliant 65 that culminated with an 60-foot eagle on the final hole.
Rahm's 13-under total earned him a three-shot win over Charles Howell III (68) and Taiwanese Cheng Tsung Pan (70).
Earlier in the day, Leishman surged into a share of the lead after six holes but a hooked tee shot on the next led to a devastating double bogey.
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He signed for a one-over 73 to fall to a tie for 20th at six under, adding to his near misses in La Jolla, including runner up finishes in 2014 and 2010.
Searching for his first US victory since the 2012 Travelers Championship, Leishman forewarned the importance of resilience at the 2008 US Open venue.
"Losing confidence is not good around this place. It's hard to score; it can go the wrong way really quickly," Leishman said prior to his final round.
Rahm became the first golfer to win at Torrey Pines with an eagle on the final hole since Tiger Woods in 1999.
"To be able to get my first win on Tour at such an iconic course, remembering all the great shots that Tiger and Phil (Mickelson) hit at this golf course, it doesn't get much better than that," said Rahm.
Next best of the Australians was Cameron Smith, who signed for consecutive weekend 70s to finish at four under and in a share of 33rd.
Veteran John Senden's two-over total left him tied for 64th, while Cameron Percy was a further two shots back in 71st.
