Macari says all the "power" is now with the new United manager.
"I think the power is with David Moyes now, I don't think he'll be that desperate to keep Rooney if he's not willing to get back into the right condition," he told talkSPORT.
"Moyes is an experienced manager and knows players have to be focused on the job and be fully committed. No matter who you are, if you're not in the right frame of mind you're not going to be staying at Old Trafford.
"I think it depends on Moyes and Rooney sitting down and if they do the assurances will have to come from Wayne that he'll get back to his best, otherwise he might continue to be second-best to Van Persie."