Why is Luis Severino having trouble staying healthy?

Because Severino has a Timing problem.

However, Severino's problem is that, like James Paxton, his arm is EARLY, not LATE.

And, contrary to what Brian Cashman thinks...

It could be small and a timing issue or it could be significant

...it IS a big deal.

Luis Severino's Pitching Mechanics

2018 August 3

2017 June 22

2015 August 17

2015 August 6