I've found lots of examples of RP that can't be narrowed down to one player, especially those with 10 velocity/10 effectiveness ratings. And yes, that includes looking at defensive ratings. In the example above, fielding ratings will work to narrow it down to one.
I agree with contrarian on the position players. Since the last update, I've found that I occasionally have to widen the range/fielding numbers to get it to work. If I don't get a hit the first time on a B/B+ fielder, for example, for fielding I'll enter a range from B- to B+ and for range B to A-.