The 32-year old has been frustrated by recent omissions from the starting line-up, as covered by the Telegraph, and his relationship with Vitor Pereira is thought to have all but broken down.
Numan – who appeared 118 times for the Gers between 1998 and 2003 – feels Celtic can take advantage of the messy situation.
“The last couple of weeks haven’t been very good for him with Holland or with Fenerbahce and that can only be good for Celtic,” said the Dutchman, in quotes published by the Daily Record.
“Some players accept being on the bench and keep quiet. But others make a fuss and cause trouble and that is the worst thing that can happen for a coach because it can affect other players and divide the dressing room.
“The only way for him to react is to score a goal - he did it on Sunday and the week before - so it will be interesting to see what happens at Parkhead, if he’s still on the bench or if the manager puts him in the starting line-up.”
Ronny Deila will be hoping van Persie’s attitude keeps him out of the starting line-up as his quality remains undeniable – even into his 32nd year.
With doubts over the fitness of on-loan Liverpool winger Lazar Markovic, however, Pereria will likely be forced to swallow his pride and start with the Dutchman, ensuring Celtic’s centre-back pairing will have their work cut out.
Another former United player, in the shape of Nani, will be a threat and highlights the kind of quality Celtic will have to overcome if they are to make it out of a particularly tough Europa League group.