On-loan from Brighton, the Republic of Ireland striker has struggled to win over Gasperini so far this season.
Ahead of Roma's clash with Genoa, Gasperini was asked about Ferguson's position now that Paulo Dybala is fully fit.
"Dybala? We're talking about a top-level player, and the discussion was about him," said Gasperini. "The choice of Dybala and not Ferguson stems from the fact that Dybala is a superior player.
"When he's fit, clearly the primary objective is to get him fit and find the best setup. It's not a direct comparison with Ferguson: it becomes difficult to find another player of this quality. Then, if there are other problems, unfortunately there don't seem to be any immediate solutions. So it wasn't a question of opposing Ferguson.
"If Ferguson wants to make a step forward, considering he's 21 and very young, he shouldn't focus so much on the technical aspect, where comparisons are impossible, but on the willpower, the hunger, the desire to get there, to understand where he is and perhaps to take over the role with these weapons, which are more congenial than Dybala's.
"I understand that sometimes it's difficult to distinguish things, but that's how it is. As for the rest, the transfer market will start on the 3rd and we'll see. I don't want to go back to July and August, , when we already avoided talking about the transfer market. Tomorrow we have to play against Genoa, a tough match."