Boro looked certain to record a Premiership win against the Red Devils for the fourth successive season as they clung to Stuart Downing’s first-half opener.

But with 10 minutes remaining, after neither Wayne Rooney nor Ruud van Nistelrooy could break down the visitors defence, Smith rose highest to nod home Cristiano Ronaldo’s cross and earn a share of the spoils.

Within seconds of Smith’s introduction, United almost levelled through van Nistelrooy, who met Neville’s cross with an excellent header which thumped back off the crossbar.

Rooney was involved in a scramble for possession with Schwarzer after Ronaldo had won a corner. Styles defused the situation with quiet word and when play resumed, Neville failed to make contact with Ronaldo’s bullet cross with the goal gaping.

Ten minutes from time, United levelled and not surprisingly, Ronaldo was the provider, delivering another excellent cross which allowed Smith to tower above the Boro defence to head into the corner.

Neville missed another sitter as the visitors defence started to creak badly but despite more United pressure, Boro hung on.