if I didn't know better, I'd say

• if I didn't know better, I'd say: まさかとは思うが

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• If I didn' know better, I'd say he'd lost control of his broom
  （まさかとは思うが、箒の制御が効かなくなってるんじゃないか）
  J. K. Rawling, Harry Potter and the Philosopher's Stone, Bloomsbury, p. 139