And he has backed his old team-mate to tough out the trials and tribulations of being manager at the Ibrox club and make a success of the latest chapter of his career.
Robertson, who is now a coach at USL Pro League club Phoenix in the United States, still takes a keen interest in the fortunes of the Glasgow giants.
The former left-back has been impressed with how McCoist has fared since succeeding Walter Smith as boss nearly three years ago.
And the 45-year-old believes he has the mental strength needed to withstand the intense scrutiny and lead Rangers back to the forefront of the Scottish game.
He said: "I still follow how Rangers are doing back home pretty closely online over here and it amazes me when I see the criticism Ally gets sometimes.
"His team is unbeaten in the league this season and is still involved in two cup competitions.
"It would be a tremendous feat for Rangers to reach the Scottish Cup final this season. It would be a huge achievement for the club. But Ally still gets criticised for performances and results! I don't know what more he can do.
"Everybody expects them to win League One this season. I am sure the same will be true next season when they go up to the Championship.
"So when they do these things Ally doesn't get any praise because it is simply what is expected of them. But it has always been that way.
"When I was at Rangers if we won a league and cup double it was considered a disaster. Even if you won a treble people said: 'Well, you should be doing it anyway!'
"Yes, Ally has a full-time squad in what is largely a part-time league and a large wage bill, but I still think that he has a tough job.
"The club is still getting 40,000 to 50,000 people coming to their games every week. There is a lot of pressure on him for the team to perform.
"I have managed at lower league clubs, at Elgin City and Montrose, without that number of fans and you still feel the pressure."
Robertson added: "If you are second at Rangers it is not good enough. At some big clubs you might get away with third or fourth. Not at Rangers though.
"I don't think there is any club out there where the pressure is so intense. But Ally has dealt with that pressure for all of his life.
"When Graeme Souness was in charge at Rangers he tried to force him out. But Ally loved the club so much he stayed where he was and fought his way back in.
"Then Ally broke his leg and everybody said he was finished. But he came back from that as well and was as good as he ever was.
"It says a lot about his character that he can remain so upbeat with everything he has to deal with.
"There is nobody I would rather have in charge of Rangers at the moment."
Scotland international Robertson won six Scottish titles, three League Cups and three Scottish Cups in the seven years that he spent as a player at Rangers.
During that time, the cultured defender also played alongside Light Blue legend Ian Durrant.
And he reckons there is no better man to help McCoist get Rangers back to the top flight than the former midfielder.
Robertson said: "Ian is a real character and real Rangers man as well.
"I am sure it will hurt him to see the club in the situation they are currently in and he will be keen to get them out of it along with Ally.
"Ally and Ian will be doing everything they can to take Rangers back to the Premiership.
"Ally was full of records as a player. So who knows? Maybe he will be a record breaker as manager as well.
"Maybe he will be the first Rangers manager to win every league in Scotland."