"Blockage" is baloney. The better player plays. In the case of MAT, he turns 32 at the end of March, a perfect bridge to Hassell. If Hassell is ready. Robles makes only $2 million a year less than MAT, and Robles has no baseball skill except to catch fly balls.
Doesn't seem to be for some guys. Dusty Baker, in particular, comes to mind as a guy who would happily play the cold vet over the hot rookie every day and twice on Sundays