It seems João Félix had a poor performance and his performance was weak enough to make Xavi mad at this player. Before João Félix joined Barcelona he said how loved this team and he wanted to play for Barcelona but this player mostly couldn't have good performances since he started playing for Barcelona,
In the game between Barcelona and Almería, the performance of João Félix was weak enough to make Xavi not use this player in the best squad in the game against Las Palmas.

You are right, I believe, in that Felix's performance was not strong enough to convince Barcelona to sign him on a long-term basis. However, we also need to be aware that not only Felix's performance is lacking in Barcelona; all of the team's players are struggling this year. Let's take a look at Lewandowski's goals as well. He hasn't scored as many as ten goals this season because he hasn't been able to replicate his winning ways and Barcelona pride from the previous season.
Xavi needs to be patient with the players because not only the Barcelona team is struggling this season; he should be grateful that he is even holding onto fourth place in the league table. Real Madrid was able to play well last season without complaining, and they then made an attempt to assemble a young team, which has allowed them to perform well. As for the Barcelona team, I don't see anything wrong with them because I think their performance will secure a spot in the champion league the following season.
In my opinion, there is no weak game against Joao Felix is just that sometimes he can't enjoy some matches and you'll think his performances are weak when Felix first arrived at Barcelona, everyone said he was doing well, and I believe Barcelona wants to make Felix a permanent transfer with cancelo, if you look at the matches Felix didn't play, you'll see Barcelona will not win, unless they draw. Barcelona's concern is that Xavi needs to sign another striker before the transfer window ends. And they have a match against Palmas this week, which I believe will be a cheap game for them because Palmas are not really talented enough to compete with Barcelona in the league, but if Palmas defeats Barcelona i will say xavi did not deserve to be a coach for the club. Since Girona upset Barcelona, the teams are no longer comparable they are disoriented and cannot compete with Real Madrid this season but since the league is not over, I believe they can regain their true form and win the laliga title

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