[Free]

I received a little booklet about Matchpoint Tactics, and I already had doubts about the first hand illustrated. Here it is.

You have:

Scoring: MP

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The auction went (opps silent):
1♣ - 1♦
1NT - 3NT

LHO leads a small ♥ to the 9 and your J. Before playing on ♦ you cash ♥K as well.

Now the question: how do you play your ♦s? Do you go for the safety play by ducking a ♦, or are you going for everything by cashing your top ♦s, risking your contract?

[bluecalm]

Safe play because you already got friendly lead and on average you will beat people who try for 3-3 break anyway (because 4-2 is more likely).
Seems really basic to me. Am I missing something ?

EDIT:

I guess the argument for playing ♦'s on top can be made. If you are somehow sure almost everybody is in 3NT and that people in general will receive different lead than you then you may try to beat all of them by playing ♦'s the same way as them (having extra ♥ trick).
For that to work though you basically need to have mind reading skills.
It's possible for example that everybody will receive this ♥ lead. Then if you play diamonds on top you will be making -EV play.
There is also thing about going +. People do many stupid things like being stack in partscore. You need +400 to beat them.

[lmilne]

lol yeah, duck, i don't want to go minus and it's simply playing the favourite.

i bet the booklet says to try for the maximum number of tricks or something dumb...

[MFA]

Quack

[Pict]

Cash - 8 or 10, probably beats more opponents. But I'll never be a great MP player and would duck.

[awm]

While the contract seems normal, the auction may not have been. Some people will rebid 2♣ with the south hand, or will be playing Walsh-style where the 1NT rebid may include a four-card major. In either case north is likely to bid 2♥ at second turn. This sequence makes a heart lead substantially less likely, since many tables will have an auction in which spades are the sole unbid suit.

Supposing that we received a spade lead, the only real chance to make is to play for diamonds to divide 3-3 (coming to five diamonds, two hearts, two spades). The heart finesse also appears to be losing, so we don't need to worry about a possible overtrick (winning the lead, diamond up, heart to jack, cash heart king, diamond up and run the diamonds would produce an overtrick if heart hook is on and diamonds divide).

Thus "the field" receiving a spade lead will play diamonds from the top, making 9 tricks if they divide and 8 tricks if they do not.

If we play diamonds from the top, we make 10 tricks if they divide and 8 tricks if they do not. This beats the field when diamonds divide and ties them when diamonds fail to break.

If we duck a diamond, we make 9 tricks all the time. This ties the field when diamonds divide and beats them when diamonds are 4-2.

Since diamonds 4-2 is more likely, I think ducking a trick is right.

[fuburules3]

EDIT: What I said made no sense.

[kenrexford]

4-2 is more likely than 3-3. Seems like a simple duck in diamonds to me, also.

[Free]

The book says that the lead gave you an advantage (because of the auction) and you should keep it. So you duck a ♦ to be almost sure of 9 tricks. If ♦ split 3-3 you gave your advantage away, but if they split 4-2 you keep your advantage.

My mistake was that I only counted 7 tricks for other pairs in case ♦ didn't break so you'd keep your advantage every time by playing like the field. But indeed they have 8 (reading in bed zzz)!

So it's correct to duck a ♦. 48% you'll keep your advantage, 35% you'll give it back. But if you play for 3-3 you'll only keep your advantage only 35%.

[MFA]

kenrexford, on Aug 11 2010, 03:04 AM, said:

4-2 is more likely than 3-3.  Seems like a simple duck in diamonds to me, also.

Yes, I don't think there is more to it. By ducking we will make the contract as often as possible and we will make the percentage play in diamonds.

We don't need to try to divine what is happening at the other tables (which is generally so rarely necessary imo).

[bluecalm]

Quote

The book says that the lead gave you an advantage (because of the auction) and you should keep it. So you duck a ♦ to be almost sure of 9 tricks

It's the other way around.
If you think lead gives you advantage the way to keep it is to play diamonds the same way as field does.
If you are somehow sure that ♥ lead will be very rare and that field will be in 3NT then you should play diamonds on top because that's the way field will play so you will beat them all with your extra ♥ trick.

Unfortunately you can never be sure of those things.

[Free]

bluecalm, on Aug 11 2010, 11:02 AM, said:

Quote

The book says that the lead gave you an advantage (because of the auction) and you should keep it. So you duck a ♦ to be almost sure of 9 tricks

It's the other way around.
If you think lead gives you advantage the way to keep it is to play diamonds the same way as field does.
If you are somehow sure that ♥ lead will be very rare and that field will be in 3NT then you should play diamonds on top because that's the way field will play so you will beat them all with your extra ♥ trick.

Unfortunately you can never be sure of those things.

I think you're wrong, the same way I was wrong. If we look at the figures, it will become clear. We expect that the ♥ lead will be quite rare, so we can suppose we have an advantage from the lead.

Say you play for ♦ 3-3 (35%) and they split 4-2:
you'll make 8 tricks: 3♥, 3♦, 2♠
others will also make 8 tricks: 2♥, 4♦, 2♠ (unless they play needlessly for the ♥ finesse as well).

Say you play for ♦ 3-3 (35%) and they split 3-3:
you: 10
others: 9

Say you play for ♦ 4-2 (48%) and they split 4-2:
you: 9
others: 8

Say you play for ♦ 4-2 (48%) and they split 3-3:
you: 9
others: 9

Conclusion:
- if you play for 4-2 you'll win 48% of the time
- if you play for 3-3 you'll only win in 35% of the time
So you'll win more by playing for a 4-2 distribution.

[bluecalm]

Yes, right.
I forgot that without ♥ lead you make 4♦ tricks if you play them on top.