United overturned a two-goal deficit thanks to Paul Pogba's quick-fire brace in Saturday's memorable 3-2 victory over Premier League champions-elect City, who were forced to wait to seal the title.
Herrera impressed for Jose Mourinho's men, though footage has since emerged of the Spanish midfielder appearing to spit on the City crest on the ground as both teams made their way down the tunnel for the half-time break.
Those claims, however, were swiftly denied, with a United spokesperson saying: "Ander has seen the footage of the incident and is mortified at any suggestion that his actions were deliberate.
"It was entirely accidental and there was no intent whatsoever."
It was a remarkable clash in Manchester, where United sensationally spoiled City's Premier League party.
City were up 2-0 at the interval courtesy of Vincent Kompany and Ilkay Gundogan, and Pep Guardiola's pacesetters were unfortunate not to be further ahead following the opening half.
United emerged from the break with renewed belief, however, as they stunned City — Pogba scoring twice within 97 seconds to restore parity before Chris Smalling completed the comeback in the 69th minute.