Jenn and I won a two-session sectional pairs event this weekend, but since our margin of victory was less than a board, we might not have if we hadn't gotten this hand right. It illustrates how different matchpoints is from IMPs or rubber bridge. I held, in third seat with both vulnerable:
Jenn dealt and opened 1 Club and RHO doubled. We play that whenever we have enough to respond over an opening bid, we usually make the same bid if there is an intervening takeout double. I therefore bid 1 Heart. LHO bid 2 Diamonds, Jenn bid 3 Clubs and RHO passed. I was happy in this spot so I passed. LHO now competed with 3 Spades, which was passed to me. What now?
I thought that it was likely that 3 Clubs would have made for +110 or maybe +130. If I sold out to 3 Spades, we would have gotten a bad matchpoint score even if we set it a trick, since +100 would lose to all pairs allowed to play 3 Clubs. So I had to do something. I decided that it was more likely that we could beat 3 Spades than make 4 Clubs. LHO's bidding marked him with 5 diamonds and 4 spades, and RHO couldn't have more than 4 spades (if he had 5, he would either have overcalled 1 Spade or bid 3 Spades over 3 Clubs if his hand was too strong for an overcall.) So I knew that they had at most 8 spades between them, so we had the law of total tricks on our side and they were getting a bad trump break. So I whacked it. This is a bid I would never risk at IMPs, since if they make it, we'd be -730 for a huge adverse swing.
Everyone passed, Jenn led the ace of clubs and dummy tabled:
I encouraged a club continuation. The ace held, declarer dropping the queen, but the second round was ruffed. Now I had a pretty good picture of the hand. LHO was 4=3=5=1 or 4=2=6=1. Jenn probably had the ace of hearts along with AK97543 to justify her 3 Club rebid. So to beat this, I had to score the ten of spades for our fifth trick.
Declarer played a spade to the queen. I now had the hand set since I could win with the king, play the ace and a small spade, which declarer would have to win with the jack, setting up my ten, with the ace of hearts for our fifth trick. +200 was worth 14 out of 17 matchpoints. +100 would have been considerably below average.
Declarer could not make this no matter how he played it. Probably his best chance would have been to play a diamond to dummy and a low spade. I would have to play low, then he would finesse against my ten by playing low from his J986. However, he could never shut out my spade ten. If he continued with the spade Jack or got to dummy again to play another low spade, I would win with the king, cash the ace, and then play my last club, forcing dummy's queen. If he abandoned trumps, I would eventually ruff a diamond with the ten.
It is noteworthy that RHO could have put more pressure on me by raising to 3 Diamonds. Now, while the matchpoint logic would still call for a double, it would have been much riskier for me since I would likely have faced a 9-card fit so the law of total tricks would have been working against us. I'm glad I didn't have to make that decision. As the cards were, 3 Diamonds would also have gone down since Jenn would have gotten a spade ruff. After cashing the ace of clubs, she would have shifted to her singleton spade as I would have discouraged a club continuation and spades would have been the obvious shift.