Dǎ májiàng shí nǐ de shàngjiā chū shénme pái hěn guānjiàn.
In mahjong, what your upstream player discards really matters.
Tips
usage
In mahjong, 上家 is the player to your left (who plays just before you); 下家 is to your right. By extension, 上家/下家 describes supplier/customer positions in any chain.
