防不胜防

防不胜防 [fáng bu shèng fáng]

1. ■ impossible to guard against ...; impossible to defend effectively; no way to prevent [guard against] absolutely; Precautions cannot ward off sudden attacks.; Preventive measures prove to be useless against such things.; The utmost care could not prevent it from happening.; very hard to guard against...:

他球路多变， 令对手防不胜防。 His opponent couldn't stand up to his varied and fast-changing tactics.