The 19-year-old, who played for the Magpies in the first three rounds of this year's NAB Cup, has been ruled out of action for at least the next month after being diagnosed with a left leg fracture.
He said the shin problems that kept him out until round six of the VFL last year, after he showed promise in two NAB Challenge games, had taught him the value of patience.
"It is a little bit frustrating but you just work harder at going out to get another shot to get into the seniors," he told afl.com.au this week.
"You've just got to keep playing well in the VFL so you can get your chance.
"When I get back playing pain-free, I'll just keep playing as best I can so I can hopefully get a senior game."
Sinclair admitted his lower leg had been sore for about a month leading into the VFL's round one but the problem worsened in the Magpies' season opener against Frankston on April 3.
"I don't think I got a knock or anything. It just got sorer," he said.
"Then I went to bed and woke up the next day and I couldn't put any weight on it when I tried to get out of bed, it was just that sore, and I got scans from there."
Sinclair has been told not to bear weight for at least a week and is spending his days rotating between the club, where he receives massages and gets in the pool, and the couch at home where he lives with his parents.
He said surgery hadn't been an option and the injury was expected to heal itself, with his pain level in the leg and at the site of the fracture, which is just above his ankle on the outside, the indication of whether it was getting better.
He also said his brush with shin splints last year had taught him valuable lessons on how to manage his body and strengthen his lower extremities, which would ultimately help his recovery from this setback.
"When I get back to running again, I'll be able to manage it because I had all last year with my shins, looking after them and my body to make sure they were less painful each week," he said.
"I guess it's going to be good when I get back because I'll know what I can and can't do."
He admitted he was already bored with daytime television but was enjoying the benefits of being told to stay off his feet for the time being.
"Mum's cooking me meals, so it's pretty handy," he said.
"It's probably not going to last all that long … I'll milk it for all it's worth."
