It

Pronoun

  was

Auxiliary

  due to

  be

Auxiliary

  released

Verb

  as

Adposition

  a

Determiner

  single

Adjective

,  but

Coordinating conjunction

  this

Pronoun

  never

Adverb

  happened

Verb

.

It was due to be released as a single, but this never happened.

It was due to be released as a single, but this never happened.