The 25-year-old has made 12 appearances this season after spending much of last on loan at Nice, and Ince has challenged the Frenchman to work hard to earn a place in the team.
"Elliot has to understand that he may be a very talented player, but it's not all about talent," Ince told the Blackpool Gazette. "You have to have commitment.
"There are a lot of players who are committed who would dream of having his ability, and I've told him that.
"He needs to get himself fit, train the right way and be part of what we are trying to achieve. If he does that, he'll be a very good player. If he doesn't, then he'll be sat in the pub in 10 years' time wondering, 'what if?'."
Grandin has played in two of Blackpool's last three games.