Lazio keeper Federico Marchetti injured himself celebrating after Alessandro Matri put his side ahead with a late strike and his replacement Etrit Berisha gave away the free kick which led to Sampdoria's equaliser by recklessly charging out of his area.
Lazio, who extended their winless run to seven games, were jeered off the field once again, while Ervin Zukanovic's goal gave Sampdoria their first point in four league games since Vincenzo Montella replaced Walter Zenga as coach.
Lazio, who have dropped to 12th with 20 points from 16 games, had slightly the better of a scrappy game and broke the deadlock in the 78th minute when Matri superbly headed in from Stefan Radu's cross.
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Marchetti was so delighted that he appeared to pull a hamstring as he celebrated and had to be substituted by Berisha.
The Albanian did not look comfortable, however, and a weak punch gave Carlos Carbonero a shooting chance which he sent over the bar.
Berisha's problems continued and three minutes into stoppage time, he came rushing out of his penalty area, upended Luis Muriel and was booked.
Zukanovic's free kick took a deflection off Lazio forward Felipe Anderson and ended up in the net.
(Writing by Brian Homewood; Editing by Ken Ferris)
