The Argentinian forward has gone on to become the best player in the world. He has, too, very much become Mr Barcelona.
It is only natural, then, that the Nou Camp club miss him when he is out injured. They certainly did against Celtic at Parkhead on Tuesday night.
Gerardo Martino was still able to field tremendously-gifted players like Cesc Fabregas, Neymar and Pedro up front. But none of them are Messi.
So I think Barcelona's win at Celtic Park, albeit by a narrow 1-0 margin, was massive for the Catalan club given they were missing their star player.
They are still smarting from their Champions League semi-final defeat to Bayern Munich last season.
It is one thing to lose over two legs in a knockout competition. It can happen to any side. It is quite another to lose 7-0.
It was a very painful loss for the Spaniards. Europe's premier club competition, then, is very important for them.
To win away from home without their talisman was important for a team which is changing and evolving under the guidance of a new manager.
Under Martino, Barcelona do not hold on to the ball in quite the same way that they did when Pep Guardiola and Tito Vilanova were in charge.
Having said that, they are still probably the best team in the world at retaining possession.
This Barca team, too, do no not press as high up the park when they are trying to win the ball back as they did in the past.
Two or three years ago they hunted in packs and showed incredible athleticism winning the ball back on those rare occasions they lost it.
Martino is keen for them to reserve their energy until they have the ball. He is subtely tweaking the system they have enjoyed such success with.
But with seven of the players in the starting line-up the other evening coming through La Masia de Can Planes, the club academy, he can't alter things too much.
They are all used to playing the 4-3-3 system the Spanish champions have long favoured.
I commentated on the game and was interested to see how the new Barcelona team performed. I particularly enjoyed watching Neymar in action.
He had a good Confederations Cup with Brazil in the summer and I think he will be one of the stars of the World Cup in his homeland next year.
He has tremendous natural ability. But he is still young. This is his first season in Europe and it will take him time to settle. He is one for the future.
I think Barcelona are one of four or five teams who could win the Champions League this season.
But, on the evidence of their game against Celtic, I think Bayern Munich are still the club to beat.