There are certain situations where "see" implies you met a person but in this case without context it has the nuance of simply seeing them without actually meeting them. For instance, seeing them play at a baseball game.
(a) could have the same meaning as (b), but (b) cannot have the same meaning as (a). Like Half-n-Half says, "see" may have different meanings, depending on the context. It could mean "meet". (b) is specific. (a)'s meaning depends on the context.