Like most things clutch, we tend to attach cogntive biases to our observations. We cannot help it.
One of the biggest ones is the proportionality bias, where we attach greater significance to greater outcomes. For example, the Kennedy Assassination was such a big event, it became a frame of reference. Everyone knew exactly where they were when Kennedy was shot, or when they heard about it (assuming, unlike me, you were alive then). Try that with the Reagan assassination attempt. Who remembers the date (or even the year) or where Reagan was? Not nearly as many, and it was never the point of reference. Why the difference? Reagan lived. Not a significant of an evet, so therefore not as big a deal to us personally.
Apply this to baseball. Dave Roberts' steal is a great example of proportionality bias. We have all attached massive significance to this, but very few remember Kevin Millar working the walk in the first place, and those who do certainly do not attach the same significance. Why? Probably because Millar was taken out of the game. Out of sight, out of mind. We remember Bill Mueller driving in Roberts. Big play. We remember Ortiz' walk off home run. Big, big, big play. But do you remember Ortiz popping out to 2b with the bases loaded and 2 out in the ninth inning of that same game? Why not? Wasn't that another "clutch" opportunity?
With Barnes, we remember the blown saves. We remember the bad innings. But his numbers in the ninth inning are actually about the same as any other inning. In fact, his K/BB is actually greater in the ninth inning that any other over his career except the fourth inning, which he has only pitched 5 times...