Mandeville turned game-changer when he came off the bench at Exeter City on Saturday, inspiring Doncaster Rovers to come back from 1-0 down to secure a 3-1 victory with a goal and two assists.
Ferguson has put the onus on the 19-year-old to deliver following Andy Williams’ injury, and has been delighted with his recent performances.
But he says Mandeville must now ensure he delivers regularly.
“If he plays like he did on Saturday it’ll be far easier for everyone,” Ferguson told The Star.
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“The hope with Liam is that if I was to start him this weekend, he starts being consistent.
“The good thing for him, not only did he come on, you have to say he’s absolutely changed the game.
“His team mates can see that and, as a player, that is where you really get your confidence. He knows that and that’s where he’ll get the most confidence.
“Your team mates know you’ve dug them out of a hole.
“He came on, got the goal and his two pieces of work for the other two goals were really, really good.
“Certainly, you hope if he does star, that he’s not got the belief, that confidence.
“I think if he can keep producing those performances, the boy can fly.”
Ferguson has praised Mandeville for dramatically improving his fitness and strength in recent weeks.
“Liam is a lot fitter now,” Ferguson said. “He was no where near – I mean no where near.
“He would take big lulls in sessions and games. Mainly in training, you’d be watching, he would go and then he couldn’t sustain it.
“But he’s far, far stronger physically and far fitter.
“All the players are fitter now than what they were.”
Meanwhile, reports in Kent suggest 23-year-old striker Alfie May, of Ryman League side Hythe Town, is set to join up with Rovers on trial next week.
May – who has scored 18 goals so far this term, adding to his 29 goal tally last season – has already had trial stints with Stevenage and Gillingham.