Eyebrows were raised when Marouane Fellaini was introduced as United's third substitution against Liverpool at the expense of Marcus Rashford.
Rashford's pace and penetration against the inexperienced Trent Alexander-Arnold seemed to be the more obvious switch as United chased the game.
The Reds had struggled to get around Liverpool's famed intense and high-pressing game plan and Jose Mourinho introduced Fellaini to change tack and bombard the visitors aerially.
Fellaini's arrival triggered the team's more direct approach as we hit long balls to him and Zlatan, got crosses into the box and bypassed Liverpool's dominance in midfield.
The Belgian, often a divisive and much-maligned figure at United, made the difference as his height, touch play and power unsettled Liverpool and brought about our equaliser.
His influence proved key in the goal as he rose above man of the match Dejan Lovren to head off a post, United recycled the ball and Zlatan was on hand to head in.
Fellaini scored the all-important second goal in the midweek Cup win over Hull, then signed a contract extension and the player rewarded his manager's belief in him with an impressive performance off the bench in Sunday's encounter.
Fellaini's United career has been transformed since that late penalty incident against Everton which resulted in him being booed by sections of the Old Trafford crowd against Tottenham.
He's always been something of an enigma at the club as he's produced some important moments and performs his specific role in the team very well.
His reckless approach and clumsiness can also expose him as a liability and it's this side of his game that has seen him struggle to win over a large legion of the club's fans.
Although a draw was ultimately a fair result, United were strangely out of sorts against Liverpool and earned a point through keeping things simple in the second half.
The visitors midfield trio of Giorginio Wijnaldum, Jordan Henderson and Emre Can marked tightly, they disrupted United's passing and movement and Adam Lallana completely stifled the usually excellent Michael Carrick.
United's impressive run of nine successive victories have been built on collective excellence, but all our key players failed to hit the heights of recent weeks against Liverpool.
Henrikh Mkhitaryan was quiet, Paul Pogba had a shocker, Zlatan was largely ineffective (apart from his goal) and Anthony Martial was doubled up on.
Yet despite the fact we didn't play well, the team again proved hard to beat and preserved our unbeaten run and that can only be positive.