"Ce match était vraiment le pire de ma carrière."

Translation: This game was really the worst one of my career.

[HappyPierogi]

Does anyone know why you wouldn't use a été?

Wouldn't the imparfait require additional context such as:

Ce match était vraiment le pire de ma carrière jusqu'à ...

[Josh677169]

"This game was really the worst of my career" -- not accepted as a translation. Anyone know why? Means the same thing in English as the given translation. Would that construction requre starting the sentence in French with "Ce match-là" or something?

[amaryllidoideae]

Why isn't "This really was the worst game of my career " not also right?

[NieNieNieNie]

Because it's not the same construction at all.

[Martyn413385]

When referring something in the past it would be more usual to use "That" game. Also "one" is superfluous in English, but it's not wrong.