You say he's on the decline, but he can still pull it off, right?
Literal
Decline [topic-って] say but, still can-do [agreement-よね].
落ち目 ('declining fortunes, on the way down') is casual vocabulary for someone past their prime. って言うけど is the casual pattern for 'people say X, but...' イケる is slang for 'can do it, viable, still good' — written in katakana for emphasis. よね seeks agreement. The sentence defends someone against the criticism that they're washed up.