The Sierra Leone striker is on a 12-month loan with Swedish side Elfsborg and will play at Parkhead on Wednesday night in the first leg of third round qualifying against the wishes of his parent club.
"If he knocked us out of the Champions League it would be very difficult for him to come back again," said Ledley.
"If I was in the same position as Mo I probably wouldn't play in the game out of loyalty and respect to Celtic.
"He's contracted to the club and, although he's on loan at Elfsborg, I don't think it would be the best move for him.
"Some players are different and maybe he's trying to get a reaction to prove how good he is.
"But imagine if he scored the winner. It would be a huge blow for the club and that's why he must think before he plays.
"It's massive for the players, the club and the fans.
"What we showed last season was magnificent and hopefully we can do it again this season.
"We had a fantastic run and once you've qualified it can take you anywhere. You never know."