Wasps' injury worries deepened as they started the new year with a fifth successive Premiership defeat, their longest league losing streak in 10 years.
Worcester fly-half Joe Carlisle scored the only points of the game – a penalty in each half – as his side put pressure on the home side throughout a wet and error-strewn match.
With their six-try hammering by Gloucester on Boxing Day still fresh in the memory, Wasps dominated possession and were arguably more creative but continually mishandled the wet ball, failing to score in a match for the first time since they faced Sale in 2008.
Wasps went into the game with nine players on their injury list and stand-in full-back Richard Houghton did not even make the kick-off, hurting his groin during the warm-up. With the heavy rain making footing difficult, three more players – two of them from Wasps – suffered injuries before the end of a marathon 51-minute first half.
Samoa No 8 Ezra Taylor's debut for Worcester lasted just two minutes before he had to be carried off the field, in obvious pain with a knee injury later revealed to be a ruptured patella, which will almost certainly end his season. Wasps' Christian Wade and Nick Robinson limped off with calf and ankle injuries respectively.
The result moved Worcester ahead of the home side in the table, while Wasps dropped to second from bottom and must now regroup in time for a tough trip to Leicester next Saturday. The Wasps director of rugby, Dai Young, admitted: "We're in a dogfight with four or five other teams, scrapping for our lives. There is no point panicking. Chucking all the bricks out of the pram doesn't get you anywhere. It's frustrating – we've got a great team in the stands."
Richard Hill, Worcester's head coach, said: "It's a big one for us; it means we can start to look upwards rather than over our shoulder at Newcastle. I know Wasps were under strength but they have the most potent three-quarter line in the Premiership so when we saw the rain we were pleased."
Scorers: Wasps Carlisle (2).
Wasps: Daly; Varndell, Waldouck, Flutey, Wade (Mayor, 31); N Robinson (Davis, 34), Simpson (Berry, 70); Payne, Webber, Broster, Birkett (O'Donoghue, 67), Wentzel, Du Plessis, Poff, Jones (Everard, 74). Replacements not used: Lindsay, Baker, Castex.
Worcester: Pennell; Garvey, Grove, Rasmussen, Benjamin; Carlisle, Arr (Perry, 40); Mullan, Lutui (Shervington, 57), Tomaszczyk (Taumoepeau, 26), Percival, C. Jones, Betty, Kvesic, Taylor (Abbott, 2). Replacements not used: Douglas, Gulliver, Goode, Fatiaki.
Referee: W Barnes (RFU).