Duncan Weir fired over a match-winning penalty with the last kick of the match to give Worcester a 31-29 victory over a second string Saracens.
Young scrum-half Tom Whiteley kicked 19 points to put Saracens on the brink of a remarkable win against the odds in the Gallagher Premiership contest.
However, the visitors' scrum was penalised and up stepped Weir to succeed with an angled 30-metre kick and seal a home success at Sixways.
Saracens fielded only two players, Schalk Burger and Nick Isiekwe, who were involved in last week's Heineken Champions Cup triumph but a combative performance and reliable goal-kicking from Whiteley looked to have secured victory.
Whiteley kicked five penalties and converted the two tries scored by Nick Tompkins and Marcelo Bosch.
Worcester outscored their opponents in terms with four tries, which came from Michael Fatialofa, Chris Pennell, Ted Hill and Josh Adams. Duncan Weir converted all of them to add to his decisive penalty.
Saracens took a sixth-minute lead with a penalty from Whiteley but that score was against the run of play and it was the hosts who picked up the first try.
Wynand Olivier made ground before a burst from Ethan Waller sent Fatialofa charging over the line but the score was the prelude to a period of dominance from the visitors.
Matt Gallagher burst through the defence but Burger's pass was knocked down when a try looked likely. However Saracens' period of pressure did not go unrewarded as Whiteley kicked his second penalty.
Saracens then suffered a blow when David Strettle was yellow carded for a deliberate knock-on and Worcester looked to have capitalised when GJ Van Velze crashed over the line but TMO replays showed that the Warriors' skipper had been forced into touch by an excellent tackle from Whiteley.
In Strettle's absence, Saracens were gifted a try when a misunderstanding between Weir and Ben Te'o saw the ball run loose. Tom Howe tried to recover the situation but fumbled and Tompkins was on hand to gain possession and run 40 metres to score.
Strettle had not returned in time to see the hosts score their try when a splendid long pass from Francois Hougaard allowed Adams and Pennell to combine for the full-back to score. Weir converted but Whiteley's third penalty gave Saracens a 16-14 half-time lead.
Ten minutes after the restart, Whiteley extended that advantage with another penalty before Worcester produced the best move of the match which culminated in a try for Hill.
Saracens regained the lead when a clever chip ahead from Whiteley saw Howe misread an unfavourable bounce, which Bosch collected to force his way over. Whiteley converted before adding a fifth penalty.
With four minutes to go, Ben Earl was yellow carded for a deliberate offside, with Worcester capitalising with a bonus point try from Adams before Weir's conversion and penalty left them triumphant.
