The Bhoys were held to the stalemate after going 1-0 down, having Virgil van Dijk sent off and seeing Leigh Griffiths miss a penalty during a chaotic cup tie.
Griffiths made amends by netting Celtic's equaliser - but Ronny Deila's side couldn't ultimately avoid a replay against United, the side they will also face in next Sunday's League Cup final.
And two Celtic stars in particular were the subject of criticism from McAvennie on Twitter: Forrest and Stokes.
Should have been Forrest taken off instead of Griffiths— Frank McAvennie (@MaccaFrank) March 8, 2015
Aside from the Celtic duo, McAvennie was also critical of the match official that took charge of the Cup quarter-final.
The referee was widely panned on social media during a controversial clash, while McAvennie - and also former Celtic striker John Hartson - lambasted his decisions on social media.
9/10 Cierzniak. 0/10 officials. Says it all really.— Frank McAvennie (@MaccaFrank) March 8, 2015
What's happened to the refs today why not a stern word in both players ear and leave it 11 v 11.Ridiculous decision to send both players off— John Hartson (@JohnHartson10) March 8, 2015
Celtic's treble dream remains alive - they are six points clear at the top of the Scottish Premiership. But fatigue appears as though it may be catching up with the Hoops at just the wrong time. As well as some bad refereeing displays...