[lamford]

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IMPs converted into VPs.

Two world-class players approached this defensive problem differently. West led the four of clubs, fourth best, and dummy played low. Dror Padron and Bas Drijver defended differently, although the auction was a little different in the other room. I am sure you can work out the two options; now over to you! South will play the eight of clubs on the first round, whatever you do.

[KingCovert]

I think that first instinct would simply be to play A♣, K♣ and 6♣ unblocking the suit and cashing 5 club tricks off the top! Except, if that were the solution this likely wouldn't be posted here. And, this reality is somewhat polluting my thinking. It wouldn't be strange for south to misrepresent having a doubleton in clubs if they had some other weakness.

1) North seems to have 5 cashing spade tricks.**
2) If south holds the A♥, they've got 3-4 cashing heart tricks too.
3) If south holds the Q♣ and A♥, declarer has 9 tricks on A♣, K♣, 6♣.

**: Unless partner has JT53♠. This makes 1NT a strange rebid. I'm dismissing this possiblity.

So, let's look at a few possible layouts.

Declarer has no hope. 4 club losers and the A♥.

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Declarer needs only to establish the 2 heart tricks, and take 5 spades, 2 hearts, and 2 diamonds. This is not beatable against optimal declaration.

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This hand requires a diamond switch at Trick 2.

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This hand also requires a diamond switch at Trick 2.

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I suppose this hand fails to a diamond switch. So would any better hand without the waste in the black suits, which really means with even better diamonds. I think partner would lead diamonds though, perhaps?

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I think, what it likely comes down to is that partner has a well positioned diamond holding. I think examples like the one with KQJ♦ may well start with a different lead. Probably the best line of play is to play the K♣ at trick one, and put a small diamond on the table. The 10♦ is equally as good, but, I think it's possible declarer may misplay diamonds if we let them. Rather than banking on partner holding exactly AQ9(X)♦, I'd like to give declarer the chance to play the J♦ instead of the 9♦ over my 3♦ switch. Partner should return a club for a second finesse.

EDIT: I think it's possible for declarer to have something like AQJ♦ and a diamond switch simply does the work for declarer, where breaking clubs might be better, as declarer can't gain their second diamond trick before losing 3 clubs, 1 diamond and say the A♥. But, this is a tough one. You can easily get it wrong.

[KingCovert]

I'd like to add in this separate post that there are some opportunities to play the A♣ and then return the 6♣ in an attempt to deceive declarer into ducking allowing partner to win the J♣, partner would need the A♥ or A♦ for this line. I think a strong declarer should figure out that there is no downside to playing the Q♣ in such a position, and it can be beaten with optimal play. So, it's an interesting thought, but, I'm not sure one can reasonably entertain it.

EDIT: I suppose, there is also some merit in switching to spades and seeing of declarer squeezes themselves? I thought about this earlier and forgot (got caught up creating various layouts). I'll leave this to someone else to investigate.

[gszes]

IMHO its just too speculative to make a dia switch at trick 2. There are too many ways declarer can make 9 tricks when partner started with 5 clubs. If p began with 4 clubs I still feel our best bet is to let p take trick 3/4 since they know where they are holding an ace. Just too much to ask for hoping p began with xx xxx AQJx JTxx to make a dia switch at trick 3.

[lamford]

KingCovert, on 2020-July-15, 13:35, said:

<snip>[One could] play the A♣ and then return the 6♣ in an attempt to deceive declarer into ducking allowing partner to win the J♣, partner would need the A♥ or A♦ for this line. I think a strong declarer should figure out that there is no downside to playing the Q♣ in such a position <snip>

I think that even a strong declarer would struggle to distinguish between Jxxx opposite AKx and Kxxx opposite AJx or Axxx opposite KJx in the opposing hands. It may well just be a restricted choice problem, and optimal defence might be to win with the king half the time and the ace the other half. The downside of playing a top honour and returning the six is that partner might have Qxxx(x). However, when one stops to think of declarer's hands, he is more likely than not to have 3 clubs. If he was 2-4-5-2 or 1-4-6-2 he might bid 2D instead of 1NT.

[KingCovert]

lamford, on 2020-July-16, 08:33, said:

I think that even a strong declarer would struggle to distinguish between Jxxx opposite AKx and Kxxx opposite AJx or Axxx opposite KJx in the opposing hands. It may well just be a restricted choice problem, and optimal defence might be to win with the king half the time and the ace the other half. The downside of playing a top honour and returning the six is that partner might have Qxxx(x). However, when one stops to think of declarer's hands, he is more likely than not to have 3 clubs. If he was 2-4-5-2 or 1-4-6-2 he might bid 2D instead of 1NT.

Yeah, this was my thinking as well, but, perhaps not. I suppose it depends on the 2-4-5-2 hand, I certainly wouldn't feel inclined to rebid 1NT with a minimum and such shape. I couldn't say with any certainty, so I sort of dodged it.

I guess my difficulty here is that I don't know if partner has the A♥ or a good diamond holding. I can't know. If partner has the A♥, then, I can perhaps afford to give declarer a club trick, PERHAPS. But, if declarer has the A♥, I need to switch to diamonds immediately. And, if declarer has both red suit aces, well, I've got to pay to something, and I choose to let declarer win when partner has 5 clubs. I guess.