Overtricked

It's not clear why partner didn't bid 3 NT over 3 ♦, but here you are, playing an awkward 4 ♠ contract. To beat the field at matchpoint, you have to make one more trick than the rest of the field in notrump - that's a rather tall order.

West leads the ♣ 9, you play low from dummy and East wins the club king. To your surprise, he shifts to the ♦ 6, you play the 8, West plays the jack and you win the king.

You lead the ♠ J off dummy, which loses to West's queen, and West comes back with a diamond to East's ten and your ace. Well, that clears up that suit. You draw three rounds of trumps, showing West to have started with four trumps. You now run your diamond and spade winners, pitching hearts from dummy at this position: On the last spade, if West started with the ♥ A and four clubs, he is squeeze. Even after you pitch the ♥ K from dummy, if East started with four clubs and the AQ of hearts, he is squeezed. You also make five if clubs split 3-3, of course.

The declarer I watched play this hand found another way to make the overtrick - after drawing trumps, he led the ♥ J from hand, and West, holding ♥ A-x-x-x decided to give declarer a guess, and played low. Declarer guessed right.

This is a blind spot I personally have as a declarer - I rarely assume that my opponents will misdefend, even when the correct defense might be difficult to find. Still, this time it is wrong to play for the misdefense. It only does better when West has the ♥ A, not the queen, two or fewer clubs, and chooses to play low. In all other circumstances, the squeeze does as well or better.

Making five was worth 88.5%, making four would have been very close to 50%.