Defence theory(11): Defence against melded sets(1)

Source: http://blog.jpmahjong.net/read.php/550.htm

Starting from this hand, I'll begin discussing about defence against melded sets.

Everyone might be thinking that defence against melded sets are harder to deal with, as you don't know when the other side is in tenpai. However up to a certain degree, mentsu that are melded allows you to find out the situation of your opponent's hand. From there you can formulate better and more accurate offence and defence tactics.

Mentsu that are melded, at the very least allows you to know the following situations.

1. You can predict the yaku your opponent wants, estimate the value of the hand and then the area of waiting tiles from there. Sometimes when we know the opponent has a small value hand, we can consider not going into betaori.

2. You can know the order of mentsu forming and along with discards, you can find out the area of dangerous tiles more accurately.

Also, even though the player with melded sets cannot declare riichi, but based on the situation of the game, we can usually estimate whether the opposite side is in tenpai, this sort of tile reading is highly accurate. The following are commonly seen methods of finding out if someone is in tenpai.

1) Opponent's amount of melded sets and time
Normally, you know whether an opponent is in tenpai from the following:
a. 3 melded sets at any time
b. Several tiles change occurring after 2 melded sets
c. 1 melded set near the end of the hand
Unless the opponent is calling tiles randomly, otherwise these sort of behaviour is no different from declaring riichi.

2) Opponent's discards
The most important thing to note is whether or not the opponent has discarded tiles related to major yakus. Example:
a. Discarding manzu when making a manzu chinitsu.
b. Discarding a middle tile dora after calling middle tiles.
c. Discarding chun while it's a live tile, after having pon on haku and hatsu.

When situations like these occur, the opponent is probably in tenpai, at the very least in iishanten. Also, if the opponent continuously discards the tiles they draw or discard a very safe tile, this signifies that the opponent is in tenpai.

3) The action the opponent takes when other players attack
This sort of tile reading is useful when playing in high level games.
You can tell that an opponent with melded sets is in tenpai, when he takes the following actions even when another player takes an obvious offensive stance.
a. continue to call on tiles
b. continue to discard dangerous tiles

Of course, knowing whether or not the opponent is in tenpai is just the first step. The next step would be determining the value of the hand and the area the waiting tiles are in. This will be discussed in the next article.
(To be continued.)