Wasps rugby director Dai Young is stepping back from first-team duties "for an interim period" at the English Premiership club.
Former Wales and Lions prop Young, 52, has been in charge since 2011.
Wasps are currently ninth in the Premiership after nine games while they made a pool stage exit from this season's European Challenge Cup.
Wasps issued a brief statement which said: "Director of rugby Dai Young will be stepping back from first-team duties for an interim period.
"Lee Blackett will step up to interim head coach. Further announcements will be made in due course."
Wasps' next game is away against Leicester Tigers on Saturday.
The Coventry-based side have lost six of their Premiership matches this term, winning just two of the last four.
Young enjoyed a successful playing career with Swansea and Cardiff, winning 51 caps for Wales and playing in three Tests on the 1989 British and Irish Lions tour to Australia.
Wasps have not won a major trophy since lifting the Premiership title in 2008.
Young, though, did lead them to the 2017 Premiership final, when they were beaten 23-20 by Exeter after extra-time at Twickenham.