I can't agree. Managers do make blunders sometimes, because they're human, and their judgment can get clouded, especially in high pressure situations.
Red Sox fans saw it in 2003 with Grady.
Then in 2004 Sox fans benefited from a horrible error by Torre in Game 5 when, needing 6 outs to wrap up the series, he brought in Tom Gordon (who he had burned out from overuse) instead of Rivera-because he didn't want Rivera to throw a ton of pitches for the second game in a row. After Gordon gave up a home run and put 2 more runners on with no outs, Torre brings in Rivera after all and Rivera shows that he was quite capable of getting those 6 outs.
2 consecutive years, 2 blunders that may have cost their team the ALCS.