The Argentine was on hand to nullify a City side that had already scored over 100 goals in all competitions this season, stifling the likes of David Silva, Alvaro Negredo and more.
Typically, Mascherano's no-nonsense approach got the better of anyone that came his way, while he proved equally effective on the ball during Barcelona's Champions League win at the Etihad.
Indeed, statistics from WhoScored.com show that the 29-year-old made four tackles against City, three interceptions and four clearances - each of which were effective.
And in terms of passing, Mascherano completed 96% of his passes, achieving the same rate as Xavi (although with less than half the number of passes) and bettering everyone else in the Barca side except Sergio Busquets (and late substitute Sergi Roberto). Interestingly, the Argentine also attempted three long balls, succeeding with every one.
Another former Liverpool man did not fare so well on Tuesday, however: Bayer Leverkusen manager Sami Hyypia.
The ex-Reds defender's side endured a terrible night in their last-16 first leg, as a Zlatan Ibrahimovic-inspired Paris Saint-Germain left Leverkusen with a 4-0 win.
So bad is Bayer's plight, in fact, that Hyypia admits he may give up on the tie entirely and rest his best players during the second leg.
He told Sky Sports: "We will have to think which kind of squad we will take to Paris because we have a lot of important games in the Bundesliga.
"It was a very difficult game against very good opposition. After the red card we maybe did better with 10 men than with 11."
image: © jamesmoore