For me, the problem here is defining "ace." You have referred to four theories, then added an additional qualification, which is "a player who has shown consistency for multiple seasons while being a top pitcher in all of baseball." It seems to me that if you drop the multiple seasons test, then Santana is easily an ace. I would also argue that Liriano was an ace for one season. As a long-suffering Twins fan, I am just glad that we can even argue that a Twins starter is an ace. It makes me happy to think that we will have an ace on the mound at least once in every 5 games, so you sadden me a little when you question Santana's ace status. I also wonder when bad pitching for a while makes a starter stop being an ace. Here is an article about that: http://www.cbssports.com/mlb/news/true-or-false-its-time-to-worry-about-these-four-struggling-mlb-ace-pitchers/ Perhaps the solution is to break this down into two categories -- current aces and long-term aces?