Messi no longer has his right hand men
There is no Bonnie without Clyde, no Batman without Robin and no Holmes without his beloved Watson. In football, induvidual skill is rarely enough to take you to the highest level. There is always a leader, someone who stands out as they take games by the scruff of the neck, but even they need support from the rest of their team to achieve maximum success.
As much as people like to say he did, Diego Maradona did not win the 1986 World Cup single-handedly. It is the same for Lionel Messi who, while winning everything that he has, was ably backed up by two of the finest midfielders ever to play the position. Xavi and Iniesta were two crucial pillars in the Argentine's development as a player and his rise to the top of the game.
Taking this into account, it's understandable why Messi has not been as electric in the last three years. The Barcelona forward has been without his two sidekicks. Some players, like Messi, remain at Barca and are untouchable in their positions, but the midfield has seen a lot of chopping and changing. Those who gave him the best service, those who freed him and found him in the best positions, have left. Xavi left for Qatar and Iniesta looks to be following him out the exit door now. They won everything together, and the footballing world fell in love with them. With the trident now broken forever, a little of the magic has been lost.
He continues to be arguably the most decisive player on the planet, but you can't win the Champions League alone. Atletico, Juventus and now Roma have proved that. Iniesta is not the player he once was and Messi has been adversely affeted. The looks on their faces after the disaster in Rome were poems reflecting the sadness at not being able to accomplish it [winning the Champions League] again. Barcelona are still at a loss as to how to replicate the team that Guardiola built and climb back to the very top of world football. There are no other Xavis and Iniestas in the world and they are struggling to find suitable replacements.
For now, Iniesta is still thinking about saying goodbye, and Messi could be faced with having to reinvent himself. Valverde seems to prefer reenforcing on the defensive side for the moment, but that failed at the key moment in Rome. The World Cup is coming, and Messi goes into that chasing the one thing that has still eluded him in his career - success with Argentina. If he wants to attain the god like status that Maradona has, and shake off talk that he is weakened without his lieutenants at Barcelona, this would go some way to doing that.
At 30 years old, with Ronaldo still performing miracles at the age of 33 and in a new position, Messi could be forced to reinvent himself. He will need to find another band of players to help Barcelona back up, which will be one of the challenges that could shape the next 20 years for the club. Keeping one of the best players the world has ever seen and not knowing how to use him would not go down well in the history books.