Declarer mistimed the play slightly in this deal from the 2025 Spingold Teams Championships.
North’s three diamonds was a fit jump, showing a heart fit and a decent diamond suit. (I’m a fan of fit jumps in competition rather than weak jumps, but it is even clearer that, as a passed hand, you will almost never want to make a weak jump in a new suit, given that you didn’t preempt initially.)
When South did not double four spades, North reasonably took the push to the five-level, and West furnished his fourth red card of the auction.
West led a trump in an effort to protect his side-suit tricks, which South took in hand to give up a spade. West cashed the club ace and then continued trumps, and now declarer had reached a crossroads. He chose to win in hand and then try to ruff out the opponents’ spades, but that only provided 10 tricks: two trump tricks, the six remaining ruffs separately, a spade and a diamond. He had to lose a second club trick at the finish.
Declarer should have sought to establish dummy’s diamonds instead. Provided they split 4-3, the diamonds would provide two extra tricks rather than just the one he would get from spades. It is best to win the first heart trick in hand, give up a spade and then take the second heart trick with the king in order to start on diamonds. Three ruffs are enough to establish the suit, using three black-suit ruffs as entries back to dummy: two to establish the diamonds and another to enjoy the long cards.