A regular goalscorer with Halifax Town and York City while on loan, Proctor was recalled from a loan spell at Bradford City by Howard Wilkinson and repaid the new manager's faith shortly after replacing skipper Michael Gray in a switch to a more attacking formation.
The Black Cats had been almost overrun by a Liverpool side that has now taken only one point from a possible 18 but poor finishing and another heroic performance by goalkeeper Jurgen Macho saved the day.
Sunderland though could afford the luxury of a missed penalty by Gavin McCann when leading 1-0, Chris Kirkland producing a fine diving save to his left after Jamie Carragher had been harshly penalised for handball.
Liverpool produced the first shot on target in the 35th minute but a minute later fell behind when McCann beat a hesitant challenge from Steven Gerrard before taking a return pass from Tore Andre Flo in his stride and neatly lift the ball over Kirkland.
Macho saved in style from Vladimir Smicer and Baros just before the interval, again from Baros on the resumption and kept his best to keep out a Danny Murphy free-kick in the 53rd minute.
Baros was not to be denied in the 68th minute however, when he latched on to a Gerrard pass and fire past Macho for his seventh goal of the season.
Liverpool piled on the pressure only to be delivered a sucker-punch by the jubilant Proctor. He swung wildly at a pass from Kevin Phillips but made no mistake at the second attempt.