At the time, I remember being really excited for getting Greinke because we needed pitching and we were trying to make a last run with Fielder. However, I still think going all-in in 2011 was a mistake and that we should have traded Fielder when the Giants were willing to give up Bumgarner for him (https://bleacherreport.com/articles/486451-mlb-trade-rumors-prince-fielder-and-the-san-francisco-giants-are-a-perfect-fit).
Not trading Fielder in 2010 and then going all-in in 2011 gave us a really good run for 2011, but then some really bad teams in the next couple of seasons. I think that 2010-11 run for Melvin looks really bad in hindsight, especially when the Royals end up winning in 2015 with Escobar and Cain being key contributors for them.