The Spaniard's future was the subject of intense speculation as the close of the window neared on Monday, with United thought to have made a last-ditch attempt to bolster their midfield.
However, the deadline passed without Herrera making the switch to Old Trafford, with Spanish tax laws and a bogus delegation of officials from the English club all blamed in reports in the immediate aftermath of the move's collapse.
But Herrera has insisted he never reached an agreement with United, and says he therefore remained calm throughout the Premier League outfit's pursuit of his signature.
"The last 24 hours were calm. I ate with my team-mates and I was very calm," he said. "At no point did I see myself leaving. The only option, like the president said, was to pay my release clause.
"I never reached an agreement with United. It is an honour that United made an offer for me and that Athletic want me."
The 24-year-old also explained that lawyers at the headquarters of the Liga de Futbol Profesional, who were believed to be attempting to thrash out a move, were not acting on his behalf.
And, after insisting United must face questions over their inability to complete the transfer, he went on to underline his commitment to his current club.
"I won't speak about theories. I only count the things that have happened and at no point did I speak with United," he added.
"I am going to continue demonstrating my commitment to Athletic like I have from the first day that I arrived. I speak for me, not for others. The club can testify that my attitude has been fantastic.
"I am flattered to see that one of the biggest clubs in the world like United have made an offer for me."
Herrera joined Athletic from Zaragoza in August 2011, and has played a prominent role for the Basque club since.
