This deal comes from the round of 32 of the Spingold at the 2019 Summer NABCs in Las Vegas. The match featured some of the best bridge players in the world, though the players involved here (who shall remain nameless to protect the guilty) showed a lack of concentration. With only four deals left in the match, the underdog team had a 21 imp lead.
Both tables in the match played 6x and both received the lead of a high club. What would your plan be?
At one table, declarer ruffed with the 3, then played a diamond to the Q which was captured with the A, and received a spade back. He played low and with the 9 coming from LHO (a 1-1 break), he won in dummy. When he ruffed a diamond (with the K), the K fell on his left. He now played the 5 of spades to the dummy. Do you see the problem? While his J was good, the rest of the diamonds weren't established. Declarer didn’t have another way back to dummy. All of his remaining spades were higher than dummy's! He had to fall back to hoping for Kx onside and when that failed, down he went.
At the other table, declarer ruffed the opening lead high and continued approximately as our first declarer did. The difference here was that declarer had 3 dummy entries (all in spades) and was able to set up the entire diamond suit. The play was: Club ruffed high, diamond lost, spade return to the queen, diamond ruffed high, spade to dummy, diamond ruffed high (establishing the suit), spade to dummy, good diamonds. The swing of 18 imps started a last-second comeback that turned a potential upset into an upsetting loss.
The real deal:
Note that the defender did well to play low from K5. If he goes up with the K, then plays the 9, the first declarer can correct the earlier mistake and throw the 8 under the Q.
Keeping low trump for entries in such situations should be basic, so it was surprising to see an accomplished player fail to do so.