I don't think injuries are the reason for Messi's current dip in form. After all he isn't playing below his standards all season long. He has scored 8 goals in his first 7 games. So logically the injuries from last season shouldn't have any bearing on his current form. He should be over his injury from the Almeria game, too. He is training normally for almost 3 weeks and has played games against Osasuna, Milan, Madrid and Celta. He couldn't have been lacking match fitness against Espanyol. Maybe not 100 % Messi but still not the main reason why he only managed 1 shot on target against Espanyol.
No, there is something else. And if you pay attention you will notice that all recent games except Celta (where Messi was actually superb with lots of dribbles and key passes) had something in common. Milan, Madrid and Espanyol packed the middle and Tata in return put Messi on the right for the majority of those games. Under Tito but also in Pep's last season Barca's play had become extremely predictable. Messi would be in the center all the time, drop deep (very deep, too deep at times) to collect the ball, dribble 1 or 2 players, spread the ball to the wingers with a throughball, make a run into the box and wait for the return pass to score. This had become more and more the main attacking scheme of the team and because this was such an obvious and predictable setup ("feed Messi with the ball as much as possible"), most teams figured it out and the "big" teams with the proper players could defend it. If you pay attention to the PSG game last season you will see how even someone like Jallet, who is a horrible rightback normally, immediately anticipated the runs on his side and retreated whenever Messi had the ball in the center. Ancelotti had cleary told him that Messi would look to play throughballs in-behind him to start attacking moves.
What we're seeing now is simply less Messidependencia against packed defenses. The team isn't looking for Messi all the time. There is also Neymar now who can be fed with passes (Neymar had more touches than Messi last night) and a confident Alexis who isn't shy of getting into the box and pulling the trigger instead of looking for Messi. Not everything has to revolve around Messi. Put Neymar on the left and Messi on the right and the game will be automatically stretched and packing the middle becomes useless with the 2 most dangerous attackers coming from the wings. What was Ramos doing in the latest Clasico for example? He was like: "Where's Messi whom I was supposed to follow and kick around? Hello? No one there?! Ah, nevermind, meanwhile I'll elbow Neymar's face then."
Messi might take a while to get used to a role where he isn't the main fulcrum all the time who starts and finishes all the attacking moves. But for the good of the team this is really important.
So to make it short, I believe it is:
[x] No Longer Sole Point of Attack
Let's just hope Neymar doesn't release a biography next season which starts with the sentence: "Everything started rosy but then Messi started to talk." And hopefully Tata doesn't use SMS.