The answer to what happens if a player has no chances isn't just my opinion, Mike Bravard has posted the answer in the manual and elsewhere:

From the manual:

"NOTE 1 : Players who appeared at a position and are rated but did not field a chance are treated very harshly by the game - as if they were unrated or worse. DO NOT USE such players at those positions!"

So DO NOT use someone who is rated at a position with no chances. You'd be better off to play a 1B guy in the LF than a guy rated in LF but with ZERO chances.