It's true that in a last few seasons of Messi in Barcelona, their quality was lower than what they had in the past with Pep Guardiola and Luiz Enrique as their coaches and with better players, Xavi, Iniesta, Villa, Eto'o, Suarez, Neymar ... The transfer of Neymar to PSG marks a decreasing quality of Barcelona.
After that Messi carried Barcelona from scoring goals, making key passes, creating chances, controlling match intensity for them. Anyway as a single player, Messi could not bring them to success. Their defense was worse than in the past too.
Barcelona can't get the successors of Xavi and Iniesta, it is not about the decrease in Messi's performance or the bad quality of the coach's strategy. They have no good players who can control the match in the midfield line, no one who can serve Messi as well as Xavi-Iniesta. Even, after Messi was leaving and Xavi became the coach, we never see a solid tiki-taka as previously.
Sure, Messi can't make the success of Barcelona lonely. It is a football game, it is about teamwork.
Xavi is still obsessed with tiki-taka that he is familiar with but he does not have enough ingredients to build a good one with players he has. I don't see too much different in Xavi tiki taka and the past one. Barcelona are playing more directly and using more physical strength in attacking but not different than in the past. At least, they are not too productive to covert ball possession to goals.
Xavi needs time to adopt a new tiki-taka model with new players. And since Barcelona main lineup has some young players, they need more experience to play with the tiki-taka tactic effectively. Honestly, I believe Xavi will lead Barcelona to their best era again if he continues to manage Barcelona. It may be not in the near future (not in this season), but in the next few years.
The guy entered the game in the 83rd minute. He got his first yellow in 3 minutes and the second yellow came 4 minutes after that. 
