What to do about a broken rear derailleur inner cage plate? The chain on my road bike got caught in the rear cassette and as it snapped it broke one of the guide tabs on the inner cage plate of my new Shimano Ultegra 6800-SS rear derailleur. My two questions are:


How safe is it riding with this cage plate, given that it's only a guide tab? A mechanic at my LBS said that I can keep riding for a while, as long as the chain doesn't jump over the cage when I downshift.
Where can I get this cage plate without having to buy the entire derailleur?
The relevant document is Shimano EV-RD-6800-3608A (Jun.-2013-3608A), which gives an exploded view and part numbers for each of the parts of the derailleur. For the Shimano Ultegra RD-6800 SS, you're looking for Shimano Y5XH08000 for the inner plate. (This also applies to many of Shimano's other parts to find replacement pieces)

Given that you've invested in Ultegra level gear, I'd not risk it and just wait for the replacement to arrive.