6週5日目 負けるに決まっている
Determination・stance・judgment
接続：普通形＋はずだ
According to logic or schedule, probably
注意 / Note：に決まっている is subjective conviction; に違いない is a strong, well-founded guess; はずだ is a logical expectation or schedule.
比較 / Compare：Same article: 〜に決まっている／〜に違いない. These models are often mistakenly chosen for each other — carefully read the 接続 and nuances above and then decide.
よく出る形 / Common form：普通形＋はずだ。Based on SCHEDULE or logic, it may be wrong — and at that time say 〜はずだったのに／おかしいな. This is another place 〜に違いない.
電車は十時に着くはずだ。
According to schedule, the train will arrive at ten o'clock.
彼ならできるはずだ。
If it was them, they could probably do it.
注文したのは先週だから、そろそろ届くはずだ。
Ordered it last week so it should be arriving soon.