fisical condition means a lot. even if you have 99% condition for players before the game, but exhaust your players during your game (high press, man on man) and your opponent does not (low press, zonal), it is most probable that after 70 min you will not score and your opponent will.

if you go for the important games with lower than 90% condition in the start, you will most probably lose.

what Al Svanberg said is true only if you play in the league with abandoned teams. in this case you can win without caring about condition at all.