For the week, Thompson, ranked last out of the original field of 16 players, beat Larry Nelson, the No. 1 seed, in the opening round. He then defeated John Jacobs, the ninth seed, on the second day.
Next, he handily disposed of thirteenth-seeded Ray Floyd early Sunday in the semifinals, with a 4-and-3 romping.
And finally, the 54-year-old Fernandez carded a birdie-4 at the par-5 1st, the first hole of sudden-death, to edge out Thompson, the field's tenth-seed, for a first place prize of $240,000.
For Fernandez, although this win is unofficial, it is the first time he has won an event on the Senior Tour since his last victory at the 1999 Las Vegas Senior Classic. It is his fourth overall win on the 50 and older circuit.
However, it wasn't just handed over to him by Thompson.
Fernandez led throughout the majority of the day and was 2-up through 15 holes in Sunday's final round, but the match was quickly made All-Square when Thompson won holes 16 and 17, with respective scores of par and birdie.
Both players carded bogies at the par-4 18th, but Thompson's late bit of magic ran out on the first playoff hole, when he could not match a birdie by the Argentinian.
Fernandez finished the season at 23rd on the official money list with $758,048. While he did not win in 27 starts, he did make every cut but one, and recorded six top-10s, including runner-up finishes at the Royal Carribean Classic and the Nationwide Championship.
The unlikely victory this week surely comes as a nice conclusion to his season.