Players with a 150 average and no stats indicate that they have only played in head to head rounds which do not count toward a player's average and stats. In head to head games players will still earn XP toward their level, but since it is not a ranked round, it will not count toward their average and stats.
For the first several tiers there are certain levels that will force players to the next tier. This is so you don't see high level hacks or amateurs.
_CHAMPION