Mirth semi finals isn't where you start that sort of shuffle. MLS is key to that midfield exactly through that left back position. His ability to carry the ball into and through pressure, and with his passing from deep break through lines won't be as effective playing in an advanced position.
And his surgeability helps keep his defender in the midfield honest, which makes them tuck in, freeing up Martinelli.
And then we also lose a lock down defender.
Now why you wanna go and do that, and do that?