。
It's not as though Tanaka's abilities are the only thing going for us.
Literal
Nothing Tanaka-[polite-さん] [gen-の] ability [subj-が] only [quot-と] say [reason-のは] not-exist.
なにも...ない is the 'it's not as if / it's not the case that' frame, where なにも is placed up front as an anticipatory negative, requiring the predicate to be negative. The use of オンリー as a casual-slangy substitute for 唯一 'unique / sole' — a loan deployed for stylistic color. ~というのはない 'it's not that one would say X' is a doubled-up negation emphasizing rejection of a claim.