The 34-year-old, who signed from Sussex rivals Bognor Regis Town last week, suffered the injury whilst at the Rock last season, ruling him out since January.
The Hornets' record appearance holder looks unlike to appear for The Camping World Community Stadium outfit until the start of 2020 and Di Paola won't 'rush' the midfielder's recovery.
He said: "At the moment, from a selfish point of view, we can't really consider him. He's got to do his rehab properly and he's old enough, experienced enough and clever enough not to rush back.
"I'll be far more excited when we know we've got him available to play and he's at his best. I want him to really be certain he's ready.
"He's been out since January so he's got to get himself right and he's got to see how he goes over the next few weeks. We can start getting excited about it when it's a bit nearer the time.
"You've got to not rush and put him under any pressure to come back in because he had a bad injury. If he comes back too early and does it at his age it's going to be very hard for him and it would be an absolute killer considering he's worked so hard to get back."
Charman has spent over 20 years at his hometown team, both as a player and a manager, and has made an unprecedented 500 appearances for Horsham across three spells.
Di Paola sees the midfielder's experience at Isthmian Premier Division level as invaluable and hailed Charman as 'a good leader'.
He added: "He's a good leader. You have to look at our squad and look at how many of them have played a lot of games at step three.
"If you go through the side, Will Miles has played a few games, Harvey (Sparks)'s played a few games, Mets (Steve Metcalf) has played a few games, so there's not a huge amount of experience.
"We're really excited about it. I don't know him very well but whenever I've spoken to him, he's always seemed like a really good bloke."
The Hornets undertake their longest league trip of the season on Saturday as they visit Brightlingsea Regent.
Horsham's visit to Essex will see them make a 220 mile round trip that will take them approximately six hours.
Di Paola was not phased by the length of Saturday's trip but revealed that he 'hated travelling away'.
He said: "Unless we get stuck in traffic or something, it is what is is. We get on the coach and the boys have a bit of a chat together
"I personally hate travelling anyway, hate the coaches and everything, but it's part of the season and part of the games we have to play.
"I don't think it (the length of the journey) will affect anything. We will get up there for an OK time so we can shake the legs off and go out there.
"We know we're in for a really tough game. We've had a lot of tough away games already; Enfield away, Bognor away, this Brightlingsea one away, Lewes away.
"The way I see it is, if you get them out of the way now then, later in the season, we'll have more home games
The Hornets will be without defender Harry Mills and forwards Kieran Lavery and Rob O'Toole for their game at Brightlingsea but will welcome back Metcalf.