Trafford left Burnley in July to sign a five-year deal with City, the club where he came through the ranks without making a senior appearance in his first spell.
Injury and illness to Ederson - who left to join Fenerbahce - meant he played in the first three games and he would have been confident of holding on to his position.
But he may have felt his dream move turning into a nightmare when Guardiola decided the opportunity to sign Donnarumma on deadline day from PSG for a cut price £26m was too good to turn down.
Representatives of Trafford declined to comment when asked about his future but just five months on from his return, reports, external suggest he is open to the idea of leaving again.
His appearance against Brentford was just his seventh of the season so not only is he not playing regularly, he is also having little opportunity to impress England manager Thomas Tuchel as he looks to keep his place in the squad for next year's World Cup.
The transfer to City would have come with the idea of dislodging undisputed number one Jordan Pickford, but that now appears to be a distant prospect with the Everton keeper managing a record nine straight clean sheets for England and Trafford yet to make his Three Lions debut.
"I feel sorry for Trafford," former City goalkeeper Nicky Weaver told BBC Radio Manchester. "When we signed Donnarumma, everyone was really excited about it, but I'm sure Trafford wasn't.
"When he signed, he probably thought he was going to be number one. We don't exactly know what he was told, but when you get the opportunity to bring someone in of Donnarumma's quality and at his age as well, for a relatively moderate fee, you have to take that opportunity. I feel for Trafford, I really like him.
"It's the life of a goalkeeper. I've been number one, number two and three. It's really difficult. You don't see a way into the team for him.
"He just has to stick in there, he can learn a lot off Donnarumma but I'm sure he would learn if he was playing every week."