The Rays became the Rays in 2008, dropping the Devil and rising out of mediocrity like a glorious Phoenix. Or something like that. We know they were good teams, and that the previous teams were bad teams, but now we have more composite numbers to back that up!
FiveThirtyEight recently calculated historical Elo ratings for every major league team as part of their Complete History Of MLB interactive graphic.
If you peak inside the Elo ratings for every major league team in baseball history, you'll find the Devi Rays are remarkably bad teams.