Originally Posted by Eric S.

SRAM derailleurs are very finicky. Just for the heck of it, I dug a Rival rear derailleur out of the box and put it on one of my bikes with Dura Ace 9sp DT shifters. As expected, indexing did not work. What was strange, though, was that it was unusable even with the levers set to friction shifting. It was very difficult to get the chain in just the right spot for some cogs; jumped around a lot.