"Rookie Kareem Hunt, after fumbling on his first NFL carry, scored three times and set an NFL mark: Hunt’s 239 yards in his pro debut were a record since the 1970 merger."There are several copyeditors who read TYWKIWDBI. I wonder if the above passage resulted from an autocorrect in a word-processing program or whether some style manuals would insist on this usage of "were."
If I were writing the sentence, my mind would place an unspoken (total of) before the 239 and change the verb to "was a record..."