A self-inflicted injury
In this deal from a club duplicate, only one North-South pair made four spades even though the contract was unstoppable with correct play.
At most tables, the bidding went as shown, and West led the jack of clubs. Declarer put up dummy’s king in order to try a spade finesse, losing the eight to West’s queen. A second club was taken by the ace, and the king of spades then lost to East’s ace. East returned a third club, ruffed by South with the nine.
At this point, virtually all the declarers drew West’s last trump with the jack and attempted to run the diamonds. But when East showed out on the second diamond, the contract went down the drain. Although South could ruff a fourth round of diamonds in dummy, he would have no entry to the closed hand to collect his last two diamonds. So, after cashing the A-K-Q of diamonds, these declarers next led a heart toward dummy and finished down one, losing two hearts and two spades.
At one table, though, South saw a way to give himself an extra chance if the diamonds broke 4-1. After ruffing the club return at trick five, he reasoned that if the diamonds were divided 3-2, no harm could come from cashing the A-K before drawing the last trump. If both opponents followed suit to the A-K, he could then cash the jack of spades before running the diamonds. If the second diamond happened to get ruffed, the contract was doomed anyway.
The advantage of this approach can be seen in the actual deal. When declarer cashed the two top diamonds, East showed out, but was unable to ruff. South then led a low diamond and ruffed it in dummy to establish the suit. Dummy’s remaining trump was led to the jack, and the rest of the diamonds were run. West got his heart trick at the end, and South got a well-deserved top score.