Gary Neville is disappointed with the impact Fred has had since moving to Manchester United in the summer, suggesting his former club may have overpaid for his signature.
The Brazilian was the subject of a fierce tussle between Manchester rivals United and City, before finally prompting for the red half of the city.
United paid out a fee of £50 million ($64.5m) for his services, but so far have received little on their investment.
Fred has appeared just seven times in the Premier League for his new club, prompting Neville to doubt the wisdom of his signing.
“Fred at £50m, he started the first game of the season and he looked bright, he looked tidy - but does he look like what you would expect for £50m?" the former United defender said on the Gary Neville Podcast.
“Does he change a game? Does it look like he’s going to defend your goal? Does it look like he’s going to connect back-to-front? At this moment in time, no."
Neville did concede that his old employers might yet get the best out of him, but wondered why he was not picked in Sunday's derby defeat to Man City even when Paul Pogba withdrew due to injury.
“He is still developing," Neville added.
"He’s still getting used to Manchester United and he’s coming into a very difficult position in the sense that the club aren’t the most stable at this moment in time in terms of their performance levels and the scrutiny that’s been on the club in the past three or four months.
“So, I wouldn’t put it all onto Fred but you have to ask the question, where was he [on Sunday] in that central midfield?”
That 3-1 reverse at the hands of their rivals leaves the Reds languishing in eighth place in the Premier League, a massive 12 points behind leaders City.
They also trail Tottenham by seven points in the last qualifying spot for the Champions League.