McCall wants to keep hold of the veteran goalscorer for another season, but Thorne will spend a summer of contemplation after a season blighted by injuries.
McCall told the club's official website: "It would be a no-brainer if he didn't get nagging injuries that have bothered him. Thorney's goal ratio for us has been terrific.
"If he decides there's a chance of him quitting, there's not a lot we can do, but I genuinely believe he's loved his two years here and he may want to give it one more.
"There's no rush with him. A decision won't be made in the next couple of weeks. We've had a brief chat but he always goes away for a long time and I'll speak to him again to see how he's feeling."
Thorne, 35, has averaged a goal nearly every other game for Bradford, scoring 32 in 65 starts, including 17 goals last season.