Riordan has found first team football opportunities severely limited at Parkhead since moving from Hibs, appearing only four times. Speculation earlier in the week suggested the Canaries would be interested in a January swoop, which Grant confirmed to the Daily Record.
"I like him and I'd definitely be interested if Celtic said he was available," said Grant. "I haven't made official contact with Gordon Strachan but I really liked Derek at Hibs and came up to watch him a few times at Easter Road.
"The Hibs team shapes up the way I like Norwich to play and Riordan would fit in the way he did at Easter Road," Grant continued. "I don't believe that Derek's become a bad player overnight because he can't get a game at Celtic Park. There are reasons to explain that away.
"If a manager has a team who are 15 points in front it might be that the player ahead of Derek in the queue for a game can't be left out. It doesn't mean Riordan's not worthy of a place in the side. It means the man who's already in the team's doing his job properly.
"Derek has great qualities and I'd have to be stupid not to be interested if Celtic wanted to enter into any kind of deal."