Steven Gerrard celebrated his return to the Liverpool starting lineup by converting a second-half free kick, which looked to be handing the home side all three points until Hernandez's intervention.
As a result, the Red Devils failed to produce many goalscoring opportunities during the opening 45 minutes, while up the other end Luis Suarez forced a save from David de Gea in the only real chance of note before the break.
The deadlock was eventually broken in the 67th minute from the returning Reds skipper. After Charlie Adam was brought down by Rio Ferdinand just outside the area, Gerrard stepped up to send the resultant free kick through the wall and into the bottom corner of the net.
The goal sprung Ferguson into action, and he decided to introduce the attacking trio of Rooney, Nani and Hernandez.
That change would pay off in the 80th minute, when Hernandez ghosted in at the back post to head a corner past Pepe Reina from close range.
Liverpool responded positively, with Dirk Kuyt and Jordan Henderson both forcing saves from De Gea in the United goal.
However, the winning goal would not come and both sides were forced to settle for a point apiece.