[kgsmith]

In a teams match, I found myself in the East position on the auction shown.

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Partner led the ♣2 (playing 4th best leads from length) to my ace. Assuming partner has one of the remaining aces (the ♥K does not seem helpful), and knowing my partner was unlikely to have led from the K or Q of clubs into a strong notrump, I needed to decide whether to switch to spades or diamonds. Which is the better switch, and why?

[robert2734]

If you lead a spade a partner doesn't produce the ace, the dummy's diamonds will go away on declarers KQx of clubs. If you lead a diamond and partner doesn't have the ace, dummy's spades require three pitches, C KQX D AQX(X) to make them go away. If partner has the queen of diamonds, he'll get his ace of spades later anywayz (assuming he is not leading the 2 of clubs from a doubleton).

If partner has S QJTXX H X D AXXX C XXX and you lead a spade, won't partner take the third round of spades eventually? And the answer is not necessarily because declarer can pitch a spade and a diamond on the clubs and squeeze partner in spades-diamonds.

[Tramticket]

But, surely partner has led his singleton club, so there are three discards anyway? I suppose partner could hold JXX, but the singleton looks more likely. Is that all we have to help us?

North's bidding looks bonkers.

[WesleyC]

Tramticket, on 2016-March-19, 08:08, said:

But, surely partner has led his singleton club, so there are three discards anyway? I suppose partner could hold JXX, but the singleton looks more likely. Is that all we have to help us?

A strong clue that partner doesn't have a singleton club, is that we know he is looking at a keycard. Given that he 'knows' we can't hold the ♣A it would be a poor choice to lead a singleton club.

I also don't necessarily agree with KGSmith that partner won't have a club honour. Aggressive leads against suit slams where the opponents have shown a long suit are generally considered normal.

In any case - it looks clear to switch a diamond because dummy's diamonds could easily be discarded. However dummy's 3 card spades (and our JTxx of diamonds) mean that failing to cash partner's ♠A might not be fatal.

For example if declarer holds [QJx Kx Axxxx KQx] or similar, he won't have the entries to establish and cash the long diamond but holding [AQJx Kx Qxxx Kxx] we need to cash out right away.

[gszes]

agree with the dia switch.

As an aside -- normally 1n 2d 2h 4n is quantitative and 1n 4d (texas) 4h 4n is RKC

[FrancesHinden]

robert2734, on 2016-March-18, 21:40, said:

If you lead a spade a partner doesn't produce the ace, the dummy's diamonds will go away on declarers KQx of clubs. If you lead a diamond and partner doesn't have the ace, dummy's spades require three pitches, C KQX D AQX(X) to make them go away. If partner has the queen of diamonds, he'll get his ace of spades later anywayz (assuming he is not leading the 2 of clubs from a doubleton).

If partner has S QJTXX H X D AXXX C XXX and you lead a spade, won't partner take the third round of spades eventually? And the answer is not necessarily because declarer can pitch a spade and a diamond on the clubs and squeeze partner in spades-diamonds.

If partner has QJTxx x Axxx xxx what on earth was he doing leading a club?

[kgsmith]

Thanks for the input. (1) I understand that the risk was greater that the two diamonds would be discarded than that three spades could, which suggested the greater urgency of the diamond switch. (2) On the other hand, partner figured to have more spades than diamonds (assuming, for the sake of argument, that the 1NT opener has on average 3.25 cards in each suit), so partner might be likelier to hold the spade ace.

I was unsure whether the second point was valid, and if it was, how it weighed against the first.

The opponents' bidding was bizarre, but that is how they bid it.
As it happens, partner held ♠AQxxxx ♥xxx ♦x ♣Jxx.