Manchester United are one of several clubs that have been linked with a move for the 24-year-old this season and should he make Fabio Capello's England squad for the World Cup, Cahill is only likely to attract more attention from potential suitors.
"I have always said, regardless of what club I am at, that if there comes a time when any player outgrows the football club, I won't be the person to stand in their way," Coyle said.
"I said it to my Burnley lads when I was there - if there is something better for them out there, then they would go and blossom. That will be the same with Gary Cahill."
Coyle, who has touted the centre-back as a candidate for the World Cup since arriving at Bolton from Burnley in January, is aware that it may become increasingly difficult to hang on to Cahill, but insists he would never impede the progression of a player's career.
"I have got everything crossed that Gary gets to the World Cup because if he does he will be terrific, if he is allowed the opportunity," he added.
"And if that means that he is elevated to a position where they are all going to clamour for him, then good luck for Gary Cahill."
Source: PA
Source: PA