"We all know what he's going through emotionally, but physically he's still showing up."
Interviewed after the heat, Fanning was honest about the emotional toll. "I'm walking down and almost in tears every time I'm paddling out," Fanning said.
"A friend told me once that we can deal with anything. You've just got to do the best you can and stay true to yourself and things will happen."
Fanning's win against Slater knocked his semifinal opponent, Gabriel Medina, out of the world title race.
But Medina took his revenge in their semi, producing an impressive aerial rotation to snatch the heat in the final two minutes and knock Fanning out of the event. "That's the freakish ability of this kid," commentator Martin Potter said.
The score (6.5) the judges awarded Medina for the manouevre is already dividing fans. Pipe is traditionally a barrel-riding contest, where other moves like turns and airs aren't generally scored as high. There's no doubting Medina's air was impressive - and the judges decided it was progressive enough to swing the heat.
It left De Souza needing a win in his semifinal against local wildcard Mason Ho to win the world title - and he delivered.
De Souza scraped through a scrappy heat to make it back-to-back world titles for Brazil after Medina's win last year. The pair will now square off in today's final.
The Brazilian kept pace with Fanning earlier in the morning by defeating Josh Kerr in his quarter-final. "It's not enough, I need more," De Souza said post-heat.
Fanning produced an unbelievable ride yesterday to keep progressing through the contest in Hawaii, just hours after learning of the death of his eldest brother, Peter.
Fanning - who lost another brother, Sean, in a car accident in 1998 - broke down in tears after taking down Kelly Slater and John John Florence to progress to the quarter-finals.
"It's been a huge day," an emotional Fanning said after delivering a 9.30 on his way to a 17.30 total. I've just got some personal stuff going on at home.
"It's kind of heavy to talk about right now. I don't know, I'm just cruising, and just trying to live."
The Seven Network reported Peter Fanning had been staying at his brother's Queensland home following his recent divorce.
It's believed Peter, 43, had three children.
Fanning, 34, has endured a tumultuous year after being attacked by a shark in the final of an event at Jeffreys Bay in South Africa in July.
He showed unbelievable courage to continue surfing this year and with a win at the Hurley Pro in Trestles in September put himself in pole position to win another title.
