It's actually not Xabi but Xavi, Xabi is Real Madrid current coach while Xavi was Barcelona former coach. Personally, I think Xavi was underrated although I kind of understand that his Barcelona team then wasn't functional as of the Barcelona of now. He laid the foundation for this current Barcelona if I'm not mistaken. He brought players from the La Massia team and promoted them to the senior team, it means that he saw potential in them. Some of the current signings was still Xavi, I think this current coach Flick is actually on Xavi's team but his getting the real talent out of them. Some coaches build but don't know how to continue in using what they've built, I personally think that was the case of Xavi
Xavi was a manager I respected up until the time he left the club, he was still whom I felt Barcelona should have not let go even though the final season before he was sacked wasn’t so great for them. He has a lot of potentials in managerial skills and many of what he was trying to build to have the best squad is already manifesting in the young players he brought from the young team players of the club. If he had stayed longer, he might have gotten what he needed or maybe he might have not been still able to handle the team very well as Hansi Flick is doing now. I really love him as a manager and regardless of what happened that lead to his sack, I feel he should be commended for his efforts because part of them are playing out on the team now.