Many have already predicted the former Aston Villa manager will struggle to keep Norwich up and McCoist believes the task in front of him is huge.
He told talkSPORT: “They cannot accept relegation. No chance. I think in appointing Dean Smith they've appointed a top class manager.
“I make no apology for saying it, but I do think he was sacked a bit early at Villa.
“I do think also that if does manage to keep them up, it will be one of the managerial appointments of the decade."
Ex-Norwich striker Dean Ashton hailed the move as a 'great appointment' and felt that Smith was unlucky to get axed by Villa.
“He was unlucky to lose his job at Aston Villa, when I've looked at what has happened in the recent past there, he's lost his outstanding player that any team would miss, brought in new players, some of those have had niggling injuries and had the problems with the international break.
“It wasn't as if he's had every player available from the start of the season, he's had that issues.
“I don't think that has been taken into account with that poor run and Norwich have seized upon it.
“Delia (Smith) has barely let his tyres skid down in New York before they've phoned him up as they know he's a man who can come in there and work with exactly what Norwich want to work with, that's developing players and clearly has got experience of the Championship, as that could feasibly happen.
“I think it's a great appointment."
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