I am with Mark here. Nobody can predict the future - so I think you have to be careful when looking purely at results to evaluate whether a mistake was made. After all, if a #1 overall pick with no medical red flags wrecks his knee in the first workout - that did not make the pick incorrect, just s***** luck.
I agree, we can't say "Farrell was wrong", but we can say that he has made a lower probability choice offensively with Nava. Now could he justify it by saying Gomes gives us a better chance defensively? Yes - but he hasn't. As such, the decision can be criticized, no doubt. I mean the information for any decision here is imperfect - the question is whether you are reading the information you DO have correctly? I think you can argue that Farrell has not with the LF decision.