It can't cost

I played at the club instead of online last night, but Xwing showed me this deal (board #7) from the OKbridge 5:30 (Pacific time) ACBL mini-tournament (hands rotated):

                ♠ J 6
                ♥ A 10 7 5 2
                ♦ Q 7 6
                ♣ 9 8 5
==
                ♠ A 9 8 7 4 3 2
                ♥ ---
                ♦ 10 8
                ♣ A K Q 4

There were many auctions. Some players opened 4♠ in fourth seat. Others opened 1♠ and eventually bid game. In any event, 4♠ was a common contract and the ♥Q was usually led.

After this beginning, you are happy to discard one of your diamond losers. What now?

The majority played the ♠A and another. If you think about it, however, what can it cost to lead the ♠J? This works when East has ♠ K 10 5 and panics and covers. It also works when East has ♠ Q 10 5 and covers.

There is no combination of spades where it can cost anything to run the jack. There is one more layout of the spade suit where it makes a difference. Here are all four hands:

                ♠ J 6
                ♥ A 10 7 5 2
                ♦ Q 7 6
                ♣ 9 8 5
♠ 10                          ♠ K Q 5
♥ Q J 9 8 4                   ♥ K 6 3
♦ A J 9 4 2                   ♦ K 5 3
♣ J 10                        ♣ 7 6 3 2
                ♠ A 9 8 7 4 3 2
                ♥ ---
                ♦ 10 8
                ♣ A K Q 4

The deal was played 78 times. It was played in hearts 10 times, and in some number of spades 68 times. A heart wasn't always led. When West led the ♣J, no one that I saw took 10 tricks. When a heart was led, there were 22 times when declarer played the ♠J at trick two. I don't have much confidence in your average online player, but this was a pretty good percentage.

I am always amazed at some of the things I see when examining the scores. One East-West pair played 3♥ doubled down 500, and one pair played 5♥ down four undoubled. Go figure.

Many declarers lost a trick unnecessarily when they played the club suit and unbelievably failed to notice that after the ♣A K, the ♣9 was good.

You can look at this interesting deal and see what all the players did, if you click here.