WWYD (sort of)

[Ozball]

Ok this comes from 28th Phoenix (Firebird Goddess) Cup final (one before last) and I can't understand the reasoning for why the player discarded what he did and was wondering if anyone here had any ideas:

East 1st Round
Player: East - Yuichiro Migita
Turn: 14th

Hand:
(tsumo)

Discard Pile:




My Thoughts:
Here My thought would be to discard the or and aim for Half Flush with all sets (Toi-toi).

What actually happened:
Migita-pro discards the and keeps the . I can't understand the thinking behind this. Oddly enough he draws another the following turn and discards the other so was still aiming for Toi-toi but I'm not sure of the value of getting rid of the Souths.

So anyone got any thoughts? I have the paifu so I can reproduce all the other players discard piles if that helps.


EDIT:
Watching it again and the other two south's had been discarded already, but none of the or had, so it would still have been perfectly feasible to draw/pon them if they did come out.

[Iapetus]

With haku+honitsu and the two ankous, the hand is already worth at least 9600. And as dealer late in the hand, speed comes first. Discarding nan gives a far superior path to tenpai, still allowing you to pon/draw East and 8s while also allowing you to chi/draw 25s. That's three times as many tiles, with a tenpai two or four times better. Trying to add in toitoi for a 50% increase at best is not worth it.

[gemma]

Also, perhaps the 3 and 4 are dangerous?

[Shirluban]

Watching it again and the other two south's had been discarded already, but none of the or had

In that case, if he discards and , he would need to get one of the two remaining AND one of the two remaining . That's a pretty bad way to tenpai, and an even worst wait.
By discarding , he maximises his ways to tenpai and his chances to win the hand.