Despite his obvious brilliance, Martial's work-rate and attitude has constantly been questioned during his five-year stint at Old Trafford.
But Watford skipper Deeney thinks Martial deserves no detractors.
"How can you not like Martial? He's so sick," Martial told United We Stand.
"He scored against us, everybody said he was unbelievable. He could play the same game against Burnley and not score and he's 'lazy'. That's how fickle fans are.
"He could play really bad, have real bad touches, score two, you win 2-0, [and people say] Martial's unbelievable today. They're not looking at the footballing context. If you're looking at it from a purely football context – why's he going to chase a right-back down?
"He's not going to do that. I'm not going to lie, it's how I made a living!"
He added: "I still think they need to figure out Martial – is he playing on the left or as a striker?"