The 26-year-old's goal at Camp Nou, which set his side on to a 4-1 aggregate victory over the Citizens, also highlighted how the Catalan club's young stars can learn from the Argentinian striker to improve the side's long-term success.
His side had lost two of their last three games before meeting with Manuel Pellegrini's men, away defeats to Real Sociedad and Valladolid put a dent on the club's hopes of retaining their La Liga title—Barca now sit in third place, four points behind league leaders Real Madrid.
However, according to the Independent, Messi spoke of his belief that Barcelona are back to their best and still have high hopes of winning the league:
We were coming off two very serious setbacks away from home (at Real Sociedad and Valladolid), but more so for the performances than for the results. Here we've returned to be the Barcelona that we want, that the fans expect.
We're the first to be self-critical and we know we haven't done things well, we know when we've done badly. We lost the opportunity to continue being close to Real Madrid, but the league isn't lost whatsoever. There's a long way to go.
Messi's contribution to the cause against City highlighted his continued importance to the side, with a number of quick-minded runs through Manuel Pellegrini's side, while keeping a grip on possession by exerting Barcelona's trademark style of attractive, passing football.
His breach of the Citizens' defence came into light with Messi's goal, as he profited from Joleon Lescott's mistake to pick the ball up inside the box, allowing him to calmly chip over the head of an onrushing Joe Hart to open the scoring.
This, adding to his league form of 15 goals and bagged eight assists in 20 league matches, per WhoScored, shows just how important the forward can be in regaining the title, despite a torrid run of recent results, as he looks to get back to his prolific strike rate.
Such goalscoring prowess has placed the Argentina forward in European folklore, as tweeted by OptaJoe:
His continued form can only be of benefit to Barcelona as they look to chase down success in both La Liga and Champions League, as the club also focus on a Copa del Rey final win over Real Madrid.
Seeing such an enigmatic forward continue both to score and assist in all competitions is not only a joy to watch for football fans across the globe but also for Barcelona's young stars, who will look to take on every crumb of experience that the 26-year-old has to offer.
Young forwards such as Neymar, Pedro, Cristian Tello, Alexis Sanchez and Isaac Cuenca will be keen to carry the mantle for Messi and want to partner him as much as possible as they look to improve their own respective on-field abilities.
Seeing how the striker presents a constant threat, both by way of scoring and supplying, will give great confidence to the more fresh-faced of Barcelona's squad as they closely monitor his importance, both to Barcelona and also on the international stage.
Gerardo Martino's men take on Osasuna next time out before a must-win match over Real Madrid gives them the chance to close the gap on their fellow title-chasers; matches against Celta Vigo and Espanyol then see out March's fixtures.
The side also take on Champions League-chasing Athetic Bilbao in their run-in and then it's a gruelling home match against Atletico Madrid on the final day of the La Liga—a match which could yet decide Barcelona's title fate.