'crucial week' is correct and usable in written English.
You can use it when referring to a week that is important or significant, for example, "This is a crucial week for the team, as they will be competing in the finals."
It is a crucial week for the party.
This is a crucial week for the MetroStars.
"It is a crucial week, we are conscious of that," he said.
"The whole week is a crucial week," Devils Coach Pat Burns said.
In October he missed a crucial week of preseason training because of a back injury.
But as this crucial week gets under way, we may well face the doomsday scenario.
This is a crucial week for the fate of our seals.
Week 13 is a crucial week for many of you, a week when playoff hopes will either be bolstered or blasted.
Rumblings of discontent about May's leadership come in a crucial week for her premiership as the government publishes its EU repeal bill on Thursday.
Greece has denied being intransigent in its dealings with eurozone officials, ahead of another crucial week for the cash-strapped country.
Pochettino will be hoping the 24‑year‑old can continue to excel during a crucial week, with Spurs potentially depleted for games against CSKA Moscow and Manchester City.
