Amorim later clarified that Onana had not been dropped for this game and was also not about to leave the club.
The United boss said the Cameroon keeper had not been considered because he had missed every pre-season match because of a hamstring injury he sustained at the beginning of last month.
United did have tentative discussions much earlier in the transfer window about signing World Cup-winning goalkeeper Martinez from Aston Villa.
That went nowhere. More recently, they have been quick to rule themselves out of a move for PSG’s Champions League-winning goalkeeper Donnarumma.
In addition, United also decided to loan highly-rated 21-year-old Radek Vitek to Bristol City.
Internally, United have high hopes for the Czech Republic youth international, whose performance in Saturday’s 0-0 draw with Charlton on Saturday was labelled “world class” by Addicks coach Curtis Fleming.
However, United clearly feel Vitek is not yet ready to deal with the pressure of being a regular at Old Trafford.
So, if Onana was not available, it left Amorim facing a straight choice between Bayindir and 37-year-old Tom Heaton, who signed a one-year contract extension this summer and says he still has a “drive and desire to play”.
Amorim was displeased at being asked about his goalkeeper selection during his assessment of Sunday’s loss.
He took particular exception to a suggestion that Bayindir’s failure to keep out Son Heung-min’s corner in an EFL Cup loss at Tottenham in December, when the keeper was also crowded out in his own six-yard box, was a reason why picking him was a risk.
“Why?” he responded. “[Son’ goal was] without VAR. With VAR, it’s a foul.
“And then what happened in the next game? Who saved the penalty? Who saved the game? You don’t remember?
“Bayindir was unbelievable in that game. I consider everything to put one on another.”
There were actually four games, and almost a month, between the Tottenham defeat and the next time Bayindir played – in United’s FA Cup penalty shoot-out victory at Arsenal.
Onana started all the matches in between.
Given Amorim’s subsequent comments about his overall goalkeeping department, the chances are Onana will be back for next weekend’s trip to Fulham.
“We proved today we can win any game in the Premier League, especially against a great team like Arsenal,” he said.
“We were the better team. I’m happy with the three goalkeepers.”
