It would be the other way around where the guru will be chasing his student & it would be Hrithik saying "Jo much bhi seekha hai, aapne sikhaya hai sir".
Either way, it would have worked last decade where Hrithik was the younger superstar & Salman.Khan was the senior. Now this casting is perfect with super quick Tiger & super slick Hrithik.
To add on, if Salman Khan was cast, no matter how bad the trailer cut would be, they wouldn't dare show Salman getting beaten up throughout. You don't want to lose your audience over a trailer itself.