The Warriors accounted for Penrith 42-20 on the back of a five tries to one first-half blitz, with burly winger Manu Vatuvei grabbing a double in the space of three minutes.
But the Warriors will be sweating on McKinnon, who was seen remonstrating with the sideline official after Penrith winger Luke Rooney was awarded a second-half four-pointer off a blatant Rhys Wesser forward pass.
The touch judge then claimed that McKinnon had spat at him and the Warriors custodian was duly booked for a second time by referee Ben Cummins.
He was already on report for showing dissent towards Cummins earlier in the match.
The incidents tarnished another fine performance from McKinnon, who forced his way over for a first half try four weeks into his comeback from a serious knee injury.
They also detracted from an exciting all-round display from the Warriors, who were simply too big and too strong for the mountain men.
The Warriors sit just outside the top eight on points differential and need to beat the Eels in Parramatta next weekend and see either Newcastle or Canberra go down to taste finals action.
Warriors skipper Steve Price acknowledged it was a must-win game if his side was to have any chance of making the finals.
“We desperately needed them (the two points), it was quite obvious especially after Newcastle winning (against Melbourne) last night,” he told ABC Grandstand.
“We can’t control that, all we can control is what we do. We didn’t start as well as we wanted to but geez we came back well.
“We had a little bit of last week’s jitters, ran over the sideline and gave away some penalties.
“But then we just got back to the basics … as soon as we got that we got some ball back, started to build some pressure and got some tries.”
Price said McKinnon was frustrated with some refereeing decisions that went against the home side, but hoped he would be free to play against the Eels.
“Wade was disappointed with a couple of decisions and he spoke to the referee and he felt it wasn’t the right way,” Price said.
“Wade has just got to get back to what’s been working for him, and hopefully nothing will come out of it and he’ll be right for next week.”
The Panthers crossed within five minutes via Rooney but were then swamped by a Warriors onslaught which netted five tries in 14 minutes.
The New Zealand side went into the sheds leading 30-6 and an annihilation looked on the cards before the Panthers stopped the rot with some early four-pointers in the second stanza.
Normal service resumed however when Jerome Ropati crossed unattended out wide and then hooker Ian Henderson capped a fine individual performance by busting his way through some pathetic Panthers defence.
Rooney completed his hat-trick for the Panthers late on.
Any flickering hope the Panthers had of playing finals has well and truly been snuffed out and they suffered the further indignity of losing hooker Luke Priddis to what looked to be a serious shoulder injury late in the match.
Warriors 42 (M Vatuvei 2, M Luck, W McKinnon, M Witt, J Ropati, I Henderson tries; M Witt 7 conversions)
Panthers 14 (L Rooney 3, M Gordon tries; M Gordon 2 conversions)