The former United captain said Lukaku has “no defence” for the goal he missed.
Neville said Lukaku ‘should score’ the glorious opportunity he wasted, but admitted he had “a little bit of sympathy” for the striker.
Lukaku latched onto a misplaced backpass from Danny Rose and rounded Spurs goalkeeper Hugo Lloris.
With the empty net before him, all he had to do was stick it into the back of the empty net, but Lukaku guided the ball wide and the chance was gone.
Things went from bad to worse as Harry Kane and Lucas Moura scored for Mauricio Pochettino’s side early in the second half.
Neville admitted Lukaku’s miss could prove costly for the Red Devils.
“Look, he should score,” Neville told Sky Sports at half-time.
“I do have a little bit of sympathy for Lukaku. I feel like I would have missed it myself.
“It’s right foot, bending away from goal, [Toby] Alderweireld is coming back so it wasn’t as easy as it looks.
“If you look at it there, it looks simple. But at full speed… look, he should score.
“There’s no defence for a player of his quality. He should score and it’s a big moment in the game.
“You get the feeling at this point in the game Spurs could have gone under if United carried on as they were.”