If Im playing at my main site and see a player that Ive never seen before and have no stats on, Im not going to assume he is good because of a few reasons.
1) There are only so many "decent" regulars; and,
2) My database is massive

Throwing out the specifics [which is probably what you want], I dont think you can really make any assumptions just on their stack stize. Again though, this shouldnt be that common of a situation, but I guess when you get into it just dont assume anything.