The pair spent more than four years together at Queens Park Rangers and renew acquaintances in the fourth round tie at Craven Cottage.
Brevett will certainly not be underestimating Les, who is enjoying a fresh lease of life this season alongside strike partner Teddy Sheringham.
"Les is one of the best players I've ever played with," said Brevett. "I've only seen him on the box recently but he looks sharp, he's still good in the air and he's still going to be a danger.
"We were mates at QPR and he was good to be around but we haven't spoken for a few months."
'Sir Les's' return to form follows a long spell when he was troubled by injuries, allied to the arrival of Sheringham from Manchester United during the summer.
Brevett added: "To look at him now, you would never think he'd had problems. He's a very determined character and I can't speak highly enough of him.
"I also think he has benefited from having Teddy alongside him. He drops off and Les is big and strong and takes a lot of the stick so they are good for each other."
Rufus Brevett has picked out his former team-mate Les Ferdinand as the major threat to Fulham before Thursday's Worthington Cup clash.