I think you underestimate the number of extra bases people would take on Stevenson. He doesn't have enough arm to play CF regularly. That number would be far larger than the number of Robles baserunning blunders.
What if we add in the number of extra bases Robles gives by throwing to the wrong base? By over-throwing the cutoff man, throwing home ten steps behind the runner, and letting the batter take second?
Robles has not improved in anything. He seems unteachable.
Perhaps Rizzo and Davey are given Robles full-time starts in CF, his last chance to sink or swim as someone mentioned above.
