The teenager couldn't stop the Sky Blues from going down to a 3-1 loss at the Ricoh Arena but he did show enough promise to whet the fans appetite for the future.
Grandison got his debut in front of Elliott Ward who was struggling with a back problem and the ill Stephen Wright.
The 18-year-old did lose his marker for the opening goal but it was his response which pleased Coleman.
He told the Coventry Telegraph: "I thought after his initial mistake where the lad has come off the back of him and scored, he grew with confidence and did some good things.
"He attacked the ball well but it wasn't easy for him coming into a team that are not in the right half of the league at the minute.
"Maybe it would have been easier for him to play four or five weeks ago, but needs must.
"David Belly got 80 minutes in the reserves last week but he's not ready."