In the last two seasons, Barcelona have failed in the Champions League and also failed in the Europa League. Thus, even though Barcelona won the La Liga title last season but still, Barcelona does not have the quality that can take it to the Champions League final. So basically, Xavi only improved Barcelona's performance only for La Liga but as we already know, that Xavi still does not have the ability to be able to make Barcelona have the same good performance in all competitions. At least, I'm also not sure about Barcelona next season to be able to get good results in the Champions League, because it looks like Xavi will only continue to prioritize to match in La Liga.
However, despite the failures in the UCL and UEL, the improvement in Barcelona's squad performance in La Liga and becoming champions is an extraordinary achievement. We know that the current Barcelona players are not the same as those from a few seasons ago when Xavi and Messi played together. Xavi can do a focus to make the team more strength. If Xavi can remain consistent with his strategies, the performance in the UEFA Champions League will also improve.