The farce of the proposed transfer came on Monday night when reports emerged that three people said to be representing the Red Devils had turned up at the Spanish league headquarters, seemingly to meet the clause in the former Real Zaragoza player's contract.
The trio left an hour later, apparently unable to complete the paperwork required to finalise the deal.
However, it then transpired that United, who dealt directly with Athletic, knew nothing of the trio's existence.
When asked about that, Herrera said: "They were nothing to do with me, you'll have to ask them. They don't represent me nor do I know who they are."
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