Match Play

Forum Archive : Match Play

Playing when opponent has free drop

From:   Gilles Baudrillard
Date:   2 December 1996
Subject:   Big error of JellyFish
Google:   57vca3$

I play JellyFish at level 7.  I am leading 1-away, 4-away and we are
in post-Crawford games. JF wins the opening roll with 2-1 and plays
... 13-11, 6-5 !!!

Of course, it can't work :

- If I am unable to hit the blot on JF's 5-pt,I will just use my free
  drop and refuse the incoming cube.

- If I hit, I accept the cude and JF will start the game in a very
  inferior position: one more man back (two if I roll 6-4) and
  my back men having already started to move ...

In some of Kit's annotated matches, I have seen this error made by top
level players, but JF does not have the excuse to be tired at the end
of a long match :-)

Gilles ( 'gillesb' on FIBS )

John Quinnelly  writes:

Why is this play wrong?  Is it the opening play itself or is it
wrong at this match point?

Kit Woolsey  writes:

It is wrong at this match situation.  The reason is not particularly
obvious, and several top-level players make the same error.  Here is
what is going on:

First of all, it is clear that the person who is trailing in the match
will double as soon as he legally can, since he has everything to gain
and nothing to lose.  Therefore, this game (and the one after it, if
there is one) will be played with the cube on 2.

Given that the cube will be on 2, there is very little difference
between being ahead 1 away - 4 away and being ahead 1 away - 3 away.
In both cases, the trailer simply will have to win the next two games
(or win a gammon in the first game).

Since there is little difference between these two scores, it should
be clear what the leader's strategy is when he is doubled at the 1
away - 4 away score.  If he is the favorite in the game he should take
the double, while if he is the underdog he should pass and play
another game at essentially the same score.  The only difference is
that he can no longer afford to pass the double regardless of the
position, since this would put his opponent only 2 away, thus making
the following game the last game of the match (since once again the
cube will be turned immediately).  This is called the free drop.

Now, we can analyze the play of the opening 2-1 roll under these
circumstances.  If you slot the five point, you are hoping not to be
hit and to make the five point on the next turn.  However, you will
never get a chance to make that five point!  The reason is that if
your opponent misses the shot (and doesn't roll something super like
3-3 or 6-6 himself) he will be the underdog and will pass when you
turn the cube.  If he hits the shot you will be a clear underdog and
he will happily take the double.  Consequently, slotting the five
point can only lose, never gain.


Let's suppose we are considering two plays, both of which give you 50%
chances of winning.  However:

Play A is the gambling play.  A lot swings on your opponent's
response.  Half the time (when he rolls badly) your winning chances
will be 70%, but the other half the time (when he rolls well) your
winning chances will be 30%.

Play B is the conservative play.  Half the time your winning chances
will be 51%, while the other half of the time your winning chances
will be 49%.

Since your opponent has a free drop, he will always drop if he is the
underdog.  Therefore:

If you make play A, half the time he will drop and the other half the
time your winning chances will be 30%.

If you make play B, half the time he will drop and the other half the
time your winning chances will be 49%.

Obviously you should make play B.

This is what is going on (although to a lesser degree, of course) with
slotting the five point.  If he hits you have a big disadvantage,
while if he misses you have a big advantage (which you won't be able
to utilize).  On the other hand if you play 24/23, 13/11, most of the
time you will be pretty close to equal.  That shows why slotting is

The above is a very difficult concept to fully understand.  If you can
follow the logic involved, you are taking a giant step to becoming a
winning match player.


Ron Karr  writes:

This situation occurs ONLY when the match leader has a free drop.  It
does not apply at -1, -1 or -2, -2 or -1, -3, etc.  Only at
post-Crawford where the trailer needs an even number.

When my opponent is at Crawford, and I have an odd # of points, I want
to double at my first opportunity, since I have nothing to lose, and I
stand to win 2 points instead of 1 (or 4 points instead of 2, if
gammons are relevant).  Obvious, right?

Suppose I roll 2-1 first.  I'm not going to get a chance to double
until after my opponent plays.  We know that the splitting and
slotting plays with 2-1 are very close.  In fact, let's assume for the
sake of argument that they are exactly equal, so that normally it's a
tossup which play to make.

But what IS different about the two plays is the volatility after the
opening move.  When I split, nothing really dramatic happens most of
the time.  He has a few great numbers (doubles) and some good numbers
that give him a slight edge, after which he takes.  A lot of the time
he ends up with a slight disadvantage, so he drops.

When I slot, on the other hand, the volatility is larger.  Numbers
that hit the blot on the 5 point give him a big edge.  Numbers that
don't hit give me a big edge.

Under normal circumstances, the volatility doesn't matter; only the
equity.  But at this match score, the only games that we actually end
up playing are the ones where HE has the edge (because those are the
only ones he takes).  If I slot, his average edge is going to be
greater in the games we do play.  So it's in my interest to split and
try to reduce the volatility.

And in practice, it's even better than this, because when I split and
my opponent rolls some average number, it's often not clear who has
the edge (for example, would you take after rolling 5-3?).  But it's
easy to tell who has the edge after the slotting play.

Did you find the information in this article useful?          

Do you have any comments you'd like to add?     


Match Play

1-away/1-away: advice from Bernhard Kaiser  (Darse Billings, July 1995)  [Long message] [Recommended reading]
1-away/1-away: advice from Stick  (Stick+, Mar 2007)  [GammOnLine forum]
1-away/1-away: and similar scores  (Lou Poppler, Aug 1995) 
2-away/3-away: playing for gammon  (Tom Keith, Feb 1996) 
2-away/4-away: Neil's rule of 80  (Neil Kazaross, June 2004)  [GammOnLine forum]
2-away/4-away: cube strategy  (Tom Keith, Dec 1996) 
2-away/4-away: practical issues  (Mark Damish, Jan 1996) 
2-away/4-away: trailer's initial double  (Kit Woolsey, Jan 1996) 
3-away/4-away: opponent's recube  (William C. Bitting+, Feb 1997)  [Long message]
3-away/4-away: racing cube  (Bill Calton+, Nov 2012) 
3-away/4-away: tricky cube decision  (Kit Woolsey+, July 1994) 
3-away/4-away: what's the correct equity?  (Tom Keith, Sept 1997) 
4-away/4-away: take/drop point  (Gary Wong, Oct 1997) 
5-away/11-away: redouble to 8  (Gavin Anderson, Oct 1998) 
7-away/11-away: volatile recube decision  (Kit Woolsey, May 1997) 
Both too good and not good enough to double  (Paul Epstein+, Sept 2007) 
Comparing 2-away/3-away and 2-away/4-away  (Douglas Zare, Mar 2002) 
Crawford rule  (Chuck Bower, May 1998) 
Crawford rule  (Kit Woolsey, Mar 1997) 
Crawford rule--Why just one game?  (Walter Trice, Jan 2000) 
Crawford rule--history  (Michael Strato, Jan 2001) 
Delayed mandatory double  (tem_sat+, Oct 2010) 
Delayed mandatory double  (Donald Kahn+, Dec 1997)  [Recommended reading]
Doubling when facing a gammon loss  (Kit Woolsey, Jan 1999) 
Doubling when opponent is 2-away  (David Montgomery, Dec 1997) 
Doubling when you're an underdog  (Stein Kulseth, Dec 1997) 
Doubling window with gammons  (Jason Lee+, Jan 2009) 
Free drop  (Ian Shaw, May 1999) 
Free drop  (Willis Elias+, Oct 1994) 
Gammonless takepoint formula  (Adam Stocks, June 2002) 
Going for gammon when opp has free drop  (Kit Woolsey, Jan 1998) 
Going for gammon when opp has free drop  (Kit Woolsey, Apr 1995) 
Holland rule  (Neil Kazaross, Apr 2010) 
Holland rule  (Kit Woolsey, Dec 1994) 
Leading 2-away with good gammon chances  (Douglas Zare, Feb 2004)  [GammOnLine forum]
Match play 101  (Max Urban+, Oct 2009) 
Matches to a set number of games  (Tom Keith+, Oct 1998) 
Playing when opponent has free drop  (Gilles Baudrillard+, Dec 1996) 
Post-crawford doubling  (Scott Steiner+, Feb 2004) 
Post-crawford doubling  (Maik Stiebler+, Dec 2002) 
Post-crawford doubling  (Gus+, Sept 2002) 
Post-crawford mistakes  (Rob Adams, Sept 2007)  [GammOnLine forum]
Post-crawford/2-away: too good to double  (Robert-Jan Veldhuizen, July 2004) 
Slotting when opponent has free drop  (onur alan+, Apr 2013) 
Take points  (fiore+, Feb 2005)  [GammOnLine forum]
Tips to improve cube handling  (Lucky Jim+, Jan 2010) 
When to free drop  (Dan Pelton+, Oct 2006) 
When to free drop  (Tom Keith+, July 2005)  [GammOnLine forum]
When to free drop  (Gregg Cattanach, Dec 2004)  [GammOnLine forum]
When to free drop  (Kit Woolsey, Feb 1998) 
When to free drop  (Chuck Bower, Jan 1998) 
Which format most favors the favorite?  (Daniel Murphy+, Jan 2006)  [GammOnLine forum]

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