I had a bad hammy pull one year, it took over a month to even start practicing and didn’t get better until the next year. It sucks because you can’t rush it. So with surgery I’m not sure if that speeds up the recovery.
It seems that 9 months would be enough time so he should be good for next year. I would think he’ll be doing a lot of agility, running and stretching drills. Unfortunately, I see him focusing on getting his throwing motion down without pain so I expect the Statue of Liberty in the pocket, when he should probably be doing sprints and agility drills.