This season barcelona was very down at the start of the season, but the arrival of Xavi had actually made many significant changes, even though Xavi arrival to barcelona was a bit late but he was able to make barcelona rise and bring barcelona to finish as runner-up this season even though before Xavi arrival many people had I doubt that Barcelona will be able to break into the top 4.
I also imagine that if Xavi came sooner, of course they would be able to compete in the race for the championship and next season it looks like Barcelona will return to the way become to Barcelona used to have passion and a winning mentality under Xavi care.
You might notice that under Xavi, Barcelona were eliminated early on from the Champions League and then from the Copa del Rey. If it can still be explained that he didn't have time to get things right, then how can one explain the poor performance in the Europa League? I think next season everything will repeat itself - separate bright series of games, but in decisive games Barcelona will fail time after time (all because of the outdated Tiki Taka strategy).