Why the Discrepancy?



A K Q
8 3 2
A 9 5 3 2
9 4
J 9 7 6 5 8 3 2
Q J 10 6 7 4
Q 4 J 10 7 6
J 5 K 10 8 7
10 4
A K 9 5
K 8 Vul: N-S
A Q 6 3 2Contract: 3 no trump

When I note a discrepancy of three or four, or maybe only two tricks between two declarers in the same contract and getting the same opening lead, I think there may be three basic reasons. The first is that somebody has made a reasonable but unfortunate decision for his side. This is the unlikeliest. The other two possibilities, of course, are that either the defense or the declarer has made a serious boo-boo. Since this is under declarer play, you need hardly guess what is under discussion here. Two declarers with the queen of hearts opening lead wound up with a disparity of 3 tricks, one making 11, the other 8. Why was that?
Both declarers won the opening lead, laid down the king of diamonds and continued the suit. The winning declarer took a look at the Q of diamonds and let it hold. This was a shrewd move. If diamonds are 3-3, you've got to lose one round anyway, and letting West hold with the queen helps protect the heart suit. You could duck the lead of another heart honor, and West would be saddled with either leading into the K 9 tenace or abandoning the suit. Either way, you render the defense's holding toothless. Actually, declarer got a gift of a low heart lead, won by the 9, so that was the reason for his 11th trick (the hand should produce 10 tricks by almost any line with competent play all around). But the remaining discrepancy of two tricks was all declarer play.
The winning declarer now went to the ace of spades, laid down the ace of diamonds and then another diamond, sluffing clubs, and now was golden for 3 heart winners, 3 diamonds, 3 spades and two clubs. The losing declarer went to the ace of diamonds at trick 3, took the club hook and cashed the ace of clubs, lost a club, ducked a heart return to the 10, won the spade return and lost a diamond! East now had two top diamond winners and two top club winners, which, with the 10 of hearts, meant down one. Since declarer started with 9 top tricks (on a winning club hook), that must have been a bit of a disappointment to his partner. Declarer not only didn't develop a long diamond, but didn't even hold onto the 9 winners granted on the deal!
What went wrong? My first thought was that declarer had made the tactical error of trying to develop both minor suits. It would be a tactical error because in three no, where you expect to lose 3 or four tricks, you just don't have resources (by and large) to develop two suits -- and if you do, you'll probably find you're only developing redundant winners, throwing the long cards of one (developed) suit on the winners of the other. Or to put this another way, if you have two suits that might be developed, I'd strongly advise you to develop one for cashing before even thinking of the other.
On reflection, I'm not so sure that was declarer's intention here. Given that he didn't even retain the 9 top tricks granted on the deal with one finesse, it looks as though he may have had no particular plan in mind. Now, declarer started out very reasonably by going after diamonds with the long-card potential. Of course, at trick 4 he should lose a diamond, sluffing a club. If the suit breaks 3-3, he's golden for 11 tricks. If it breaks 4-2 while clubs are 3-3 with an onsides king of clubs, well he might get below average, but it's not a dumb error and you can be sure you'll have company -- and you can't afford to test clubs at this point anyway!
Declarer should lead a third round of diamonds, perhaps duck a heart return, another way of neutralizing the suit (and you don't know where the king of clubs is just yet), then on regaining the lead, go to dummy's spades and lose one more round of diamonds. This brings home 10 tricks (whether you duck a heart return or not). It's a fairly simple hand with obvious potential in one or the other of your 5-2 minor suits.
The declarers making 5 tricks (all with a gift, I dare say), got 95%. Those making 10 tricks (for which you don't need any gifts), got 72%. For being so careless as to go down when 9 top tricks are there, that declarer got 9%. That's an awfully big drop -- but a just one -- for kicking away two tricks. It's a simple game, my friend used to say. This hand may not prove his thesis, but it does illustrate how big points are kicked away on simple hands.

A years-later review. Perhaps I was right the first time, i.e., that declarer was thinking of developing each minor suit. It looks as though he could have picked up 10 tricks had he started at trick 2 with a focus on one minor or the other. If clubs, of course he would spend a trick getting to dummy with the K of spades. But a club finesse, cashing the ace, losing the third round leaves him with two entries to the closed hand, one to lose a fourth-round club trick and the other to cash the 5th. A heart lead from East should be ducked. Losers are two clubs and a heart. Winners are three clubs, three spades, two diamonds and two hearts for a respectable 72%.