Evans' departure in January would have arguably dented West Brom's chances of survival. But having not won a single trophy during his 17-year stint with Albion, Robertson could have empathised with Evans had he decided to join City.
"Jonny Evans has been fantastic," Robertson told Tribalfootball. "It's sad. He's made a couple of mistakes the last couple of games. But up until then, he's been one of the best players for us.
"And I was one of the ones who said it would've been sad for him to go to Manchester City at the transfer deadline, but for him, it would've been fantastic."
A tough and reliable stopper, Evans came through the academy ranks at Manchester United before spending eleven years in the first-team squad at Old Trafford.
His successful spell with the Red Devils, which included winning three Premier League titles, ended when he moved to the Hawthorns in 2015.
The Northern Irishman, who was awarded the club captaincy after Darren Fletcher's departure in the summer, has rose above the subpar performances of his Baggies teammates in what has been a disastrous season for the West Midlands club. Saturday's loss to Leicester City keeps them nine points from safety at the bottom of the table with only eight games to play.
It is likely Evans, as well as several of his teammates, will be sold if West Brom are relegated to the Championship.
Arsenal looked primed to invest in defensive reinforcements in the offseason given their paltry showing at the back this term.
Moving to a club of Arsenal or Manchester City's stature would have an impact on Evans' playing time. But Robertson believes this shouldn't deter him from joining a club that is going to challenge for silverware.
"Of course, because he's never going to win anything at West Brom, is he?" added Robertson.
"So if he goes to Manchester City, whether he is a sub or whether he plays, he'll win the league and coming up to the last few years of his career, how fantastic would that be."
You can purchase Ally Robertson's book, Thou Shalt Not Pass: The Alistair Robertson Story, by clicking on the link here.