Assuming your choice of system is natural with 5 card majors, you then have to consider the other one-level openings. Having
decided on using transfer Walsh responses to a 1♣ open, because of the benefits they bring, you need to adopt a NT strength
range that is appropriate and all you are left with is the 1♦ open. I would like to suggest that it
is not simply a matter of choosing between "4 card diamonds and a possibly short club" and "better minor but clubs if 3/3 and diamonds if 4/4", as there is more to it than that.
Consider whether you really need to show a 4 or 5 card diamond suit. I am sure the majority would open a hand within their no
trump strength range and a shape 3253 (spades first) with a bid of 1NT, and not think twice about it. They eschew showing a 5 card diamond suit in favour
of the 1NT. This is sensible, as pairs scoring favours the majors and NT over the minors - if a diamond contract makes one more trick than the NT
contract, then NT is preferred. Now think that if the 1♣ open is better
than the 1NT open as it enables you to find both NT and major contracts, then maybe you should open 1♣ on this hand ?
Follow the thought train, and you'll find that hidden, completely unexpected, benefits emerge. Let us say that we will open
1♣ with any balanced hand, or semi-balanced hand, but not a hand with a singleton.
(A 2452 shape is semi-balanced.) However, we like the benefits of our 5 card major methods, so will only do this with a 5 card minor. A six
card suit falls outside this; we will say that we will always open and rebid a 6 card suit. This means that a hand with a singleton or void will
open 1♦. Unfortunately, this may not work out well if the void is in diamonds, so we will
say that that hand has to open 1♣. The definition of a 1♦ open is therefore
either a 6 card suit, or a hand with a singleton or void outside diamonds.
Our opening structure then becomes these bids in descending order of selection. For each hand you pick up, you go through this
list from the top down and make the first call that fits the criteria. You have the values for a 1 level opening.
Open a 5+ card major.
Open and rebid a 6 card minor.
Open 1NT if the right shape and range.
Open 1♦ with any singleton or void except
Open 1♣ otherwise.
You will note that this throws more hands into the ambit of the 1♣ open than would occur with other
methods that would open 1♦. But this is exactly what we
want; we like the transfer Walsh enabled methods that follow.
The opening selection method also benefits the 1♣ open, as unless
you rebid clubs to show 6, it now guarantees at least a doubleton in each major. This ensures a 6 card major in responder's hand makes a good
contract. Without a fit, the lack of a shortage ensures an eventual NT is not unreasonable.
This method also has hidden benefits in the 1♦ open. The 1♦ open is either essentially 2 suited in the minors, or is single-suited in diamonds, or is 3 suited.
With absolutely natural responses, after a start of say 1♦ 1♠, opener with no
fit will rebid 2♣ with the 2 suited minor
hand, rebid 2♦ with a 6 card suit (responder knows this is now 6, not merely 5), or with a
shortage in responder's suit bid a natural 1NT (or 2NT depending on strength). Over the NT responder now knows it is a waste of time rebidding his 5 or 6
card suit. That alone can avoid unmakeable contracts. As the opener is known to be 3-suited, responder can safely bid any of the other suits to
You might ask "what if opener's hand is not one of these 3 types?". Well, it has to be one of those
3. Opener has at most 5 diamonds. Opener has a singleton or void in clubs or a major. That leaves 8 cards or so in the other two suits,
without 5 in a major, and therefore a fit in responder's second suit is guaranteed. After 1♦ 1♠ 1NT, responder with a weak hand and 4 hearts can safely bid 2♥ for example. Opener will be 0445, 1444, 1435 etc.
Opener will support a major if he has 4 of them, of course, but he will also support a major where he has 3 card support and a side suit
shortage. 1♦ 1♠ 2♠ could be bid on
many hands that have 4 card support, but the worst case is a 3154 shape. Should
it turn out to be a 4/3 major fit, you expect this to be playable because there are ruffs in the short suit, and, moreover, the ruffs are made in the hand with
3 trumps. 3154 is the absolute worst case, because one fewer heart would mean an extra spade, an extra diamond would cause a rebid of 2♦, and an extra club would cause a rebid of 2♣. One fewer minor would of course
mean an extra spade. One more heart, on the other hand, making the 4/3 fit a poor bid, would mean
that the hand no longer falls in the 1♦ opening category, and it would be opened 1♣.
However, note that if opener is 4351 and the bidding starts 1♦ 1♥, opener will rebid 1♠ rather than support hearts. This is
because responder may be equal length in the majors. Responder can bid diamonds or correct safely to 2♥ as he
knows opener is 4351. (Opener would rebid 1NT with short hearts.)
Playing the 1♦ open in this way means that over 90% of the time the opener
will have 4 or more diamonds, so for diamond raises you should support with a 4 card suit - inverted raises or not according to taste.
An example unbalanced diamond treatment that utilises more complex developments
Playing the natural style, as above, if as responder you have and bid a major, opener with no major will show a single-suited or two-suited hand, and then it
does not really matter what major you have. If opener has a 3-suiter with only the other major, he will bid NT. If you reply hearts you can find a
spade fit, and if you reply spades you can find a heart fit.
It does not matter which you show as you will find the fit!
Consider what would happen if you replied 1♥ whichever major you had. Opener with spades will bid 1♠ and now you can raise spades if that is your suit, or bid something else if your suit was hearts. (Opener has described
his hand as a 3-suiter short in hearts, so it is easy to pick the right contract.) Opener with a 3-suiter without spades will bid 1NT and now if
your suit was hearts you can bid 2♥ knowing you have a fit, and if your suit was spades, you pass 1NT or convert to a minor.
This means that you can reply 1♥ with either or both majors, and will always find the fit if there is one. Hey! You
now have a completely spare reply of 1♠!
You can use this as an artificial bid meaning "any hand, invitational or
better", while 1♥ means "either or both majors, but less than invitational". Similarly any reply greater than
1♠ is known to be weak.
The use of the artificial invitational 1♠ allows opener with the 1-suiter or 2-suiter to decline or accept in his first
rebid, making continuations (if any) simpler, and with the 3-suiter he always rebids 1NT. Responder can then use 2♣ as
a relay to find the short suit, and a major fit can be shown at the 2-level which is already known to be an invitation. A declined major fit plays in 2M
rather then 3M. Alternatively, a game-forcing responder can then bid the short suit to set up a GF, and subsequent bidding has more space available to explore the correct contract and level.
Develop your own responses in your own style, or contact me if my system notes would be of interest, but however you play the unbalanced diamond you will find
it pays dividends.
Ray Green (fromagegb at gmail.com) revised Feb 2016