I'm confused. He already has a secondary fastball--the sinking one. Maybe he needs a cutter? I'm still cautiously optimistic. He went from being a 97 MPH guy to a 94 guy and was a better pitcher. Has a great curve. Need to see more of the change. Remember when he threw it at 92? Well he needs one around 84/85 now.
His "secondary" fastball has always been meh. Like I said, he needs to go back to the drawing board and develop a better fastball compliment. But at age 33, and with this godawful analytics department, its pretty unlikely.
If he can possibly do it, a splitter would be the ticket for Strasburg. It'd help the 4-seamer play up both on velo and plane.
His changeup is basically a splitter. Same arm slot, same diving action.