This morning I am a Mariners fan. Give the Yankees credit, they are incredible opportunists. The A’s gave them an opening and the Yanks closed it in a New York minute.

The key turning point definitely was in Game 3, when Jeremy Giambi was thrown out at the plate on a truly bizarre play. Aside from the fact that this kept the A’s from tying the ballgame, symbolically the play told us everything we need to know about both franchises. Yankees right fielder Shane Spencer airmails two cutoff men, and Derek Jeter, hopelessly out of position, makes a spectacular catch and flip to Jorge Posada to nail Giambi.

Almost everybody screwed up on that play, and the Yankees were rewarded for it, while the A’s were punished. Spencer overthrows Alfonso Soriano, who has abandoned second base to take the throw, which is correct. But Spencer also misses Tino Martinez, who is backing up Soriano. Enter Jeter, who by all rights should be covering second in case Soriano or Martinez cuts the ball off and tries to nab Terrence Long going for two. Despite Joe Torre’s assertions to the contrary, there is absolutely no reason for Jeter to be where he was. Unless someone is going to tell me that this is a set play, where the right fielder intentionally misses two cutoff men to try and lull the runner heading toward the plate into a false sense of security. With apologies to Spinal Tap, it’s such a fine line between clever and stupid.

At any rate, on the Oakland side, Giambi fails to slide. On the one hand, I can almost see what he’s thinking: how in the heck did the ball even get to Posada? On the other, the on-deck batter, Ramon Hernandez, was in better position to see what was happening out in the field and motioned for Giambi to get down. If there’s even the possibility of a play at the plate, the runner has to slide.

Sliding on the play has two effects. First and foremost, it gives the catcher a harder target. I’d have to watch the replays again, but my suspicion is that if Giambi slides past the plate and reaches back with his hand, he scores. Or at the very least, and this is the second factor, he makes it more difficult for the home plate umpire to call him out. I really don’t understand Giambi’s decision not to slide unless (a) he was stunned that there was even a play or (b) he’s not very good at that particular skill. Ultimately, neither is excusable from a professional in that situation (not to pin all the blame on Giambi; this was a turning point, but he didn’t lose the series by himself — Oakland’s futility at the plate with runners in scoring position and complete defensive collapse in Game 5 probably were more damaging in any tangible sense).

What a frustrating end to an otherwise brilliant season for the A’s and their fans. What a frustrating chapter for all of us who are loathe to see the Yankees in yet another World Series.

Go Mariners!