"Včera nehrál dobře."

Translation: He did not play well yesterday.

[Shane820178]

"Yesterday he did not play well."

[CathyBowde1]

I thought so too and I reported it as also a correct answer.

[JovicaIgnj]

Why isn't "good" accepted and "well" is?

[VladaFu]

Although good can be an adverb as well, I am afraid this is not the right context for that.

[adelriosantiago]

Does "[ne]hrál" apply for instruments (like playing the piano) as well as a game (like playing a match)?

[Renardo_11]

Yes. When a musical instrument is specified the preposition "na" is used. Games usually are direct objects. When neither is given, such as here, it can mean both, like in English.