Poor goal-kicking cost Worcester as they missed six kicks to allow Harlequins a 41-35 win in a try-fest at the Stoop.
Warriors outscored their opponents by six tries to five to secure two valuable bonus points but a victory was well within their grasp.
They led 18-10 before they suffered crucial injuries with Quins scrum-half Danny Care taking full advantage in the third quarter to inspire his side to victory.
Care, Jamie Roberts, Mat Luamanu, Charlie Walker and Marcus Smith were Quins' try-scorers with Smith converting all five. The outside half and Tim Swiel also added a penalty.
Dean Hammond scored twice for Worcester with Perry Humphreys, Jack Singleton, David Denton, and Josh Adams also on the score sheet. Jono Lance kicked a penalty and Tom Heathcote a conversion.
Worcester suffered a setback when fullback Chris Pennell was a late withdrawal through illness. Adams switched to take Pennell's place with Tom Howe coming in on the wing.
Within four minutes of the start, Worcester suffered a further blow when they fell behind after Smith saw a gap to dart over.
Worcester soon responded when a 30-metre break from Wynand Olivier put the home defence on the back foot and when the ball was recycled, Olivier and Lance combined to send Denton in for the try.
The frenetic opening continued with a second Worcester try when a well-judged cross-field kick from the alert Lance saw Humphreys collect and just hold off Mike Brown's despairing tackle to score before a penalty from Smith brought the scores level.
Lance succeeded with a penalty, with some of Worcester's play being a revelation, as clever off-loads from the impressive Lance sent Denton and Sam Lewis into the heart of the hosts' defence and it came as no surprise when Lance provided the pass for Adams to score Worcester's third.
Lance failed with another difficult conversion and a subsequent penalty so missed kicks had lost his side nine points and when Luamanu crashed over with Smith's successful conversion Quins were only trailing by a point at the interval.
Olivier did not come out for the restart with Heathcote coming on as replacement and Lance switching to centre, while another blow was soon to come.
From a scrum 30 metres out, Worcester's scrum was shunted backwards and Care was on hand to take advantage of the disruption by pouncing to kick ahead and win the race for the touchdown.
Worcester responded with a flowing movement which should have resulted in their bonus point try. Another skilful off-load from Lance sent Joe Taufete'e flying down the middle before Jonny Arr set sail for the corner only for Care to dislodge from Arr's grasp as he dived for the touchdown.
Moments later, Arr was carried off on a stretcher after appearing to be knocked out before more enterprising play from Care set up Roberts for the bonus point try with Walker then waltzing through the home defence for the fifth.
Worcester fought to the end with Hammond scoring two late tries to earn two bonus points.