The five-time Ballon d'Or winner hit a hat-trick as Barca wrapped up the title on Sunday thanks to a hard-fought 4-2 win away to Deportivo La Coruna which saw the Catalans crowned champions with four games to spare. And the Blaugrana are on course to complete an unbeaten campaign in the Primera Division.
None of that would have been possible without Messi. In fact, it did not appear possible at all back in the summer when Neymar left the club and Barca lost 3-1 and 2-0 to Real Madrid in the Spanish Supercopa series in August.
In pre-season, Barca had played 4-3-3 with Neymar on the left, Luis Suarez in the middle and Messi on the right. But, after the Brazilian's €222 million move to Paris Saint-Germain, Ernesto Valverde switched to 4-4-2.
That gave added strength to the midfield and tightened the defence, but it made life more difficult for the forwards and, for much of the early part of the season, Luis Suarez struggled through injury and also in a new role without Neymar.
The change to 4-4-2 also made Barca more narrow, while the signing of Paulinho gave the team a player adept at timing his runs into the box, but one who offered little to the construction of attacks in midfield.
So, in many ways, Messi was left all alone. This season, the Argentine has been Barca's main scorer and also the chief creator. His hat-trick on Sunday means he now has 32 for the Blaugrana in La Liga this term and also 12 assists. But those numbers do not begin to tell the story.
Prior to Sunday's game against Deportivo at Riazor, Messi had created 78 chances for his team-mates in La Liga, given 84 lay-offs, completed 164 dribbles and had 86 shots on target, with 14 hitting the woodwork.
He had also drawn 73 fouls, many in dangerous positions and often from where he has been able to score free-kicks or penalties, although only two of his goals in the Primera Division this season have been spot-kicks.
When Barca have needed goals, he has provided them. When the team have cried out for creativity, he has produced it. When rival defences have stood strong, he has found a way through.
Back when Suarez was injured and off form earlier in the campaign, Messi scored two against Alaves, three versus Espanyol and put four past Eibar. And, when their unbeaten record looked in danger against in-form Valencia in November, he had a goal wrongly ruled out - it had crossed the line -, but still set up Jordi Alba for a late leveller.
And, in the title test against Atletico in early April, again it was Messi who made the difference as he netted the only goal in a 1-0 win with a fantastic free-kick, one of six he has scored in La Liga this season. "If Messi had been playing on our side, we would have won," Rojiblancos boss Diego Simeone said afterwards.
Then there was the game against Sevilla. Messi had been struggling with hamstring and adductor problems and had not played for Argentina during the international break, but came off the bench to rescue Barca, transforming their play and netting a dramatic late equaliser after the Catalans had been heading for a 2-0 defeat just two minutes earlier.
"Every time he touches the ball he's decisive," Valverde said after the match. "With and without Messi, the team is different."
There is little doubt about that and, as Barca claimed the title on Sunday without having lost a single game in La Liga, it was thanks in huge part to their brilliant Argentine. Because, while he has scored more goals in previous seasons, never has he been quite so influential all over the pitch as he has this term.