In my opinion Xavi is not really a terrible coach because with what he achieved at Barcelona despite managing a team that is financially struggling he was still able to lift the La Liga trophy. I also don’t want him at Chelsea but imagine what he would be able to achieve with a team that is financially stable. So with that i think Xavi will go to become a good coach in future.
I don't think that Barcelona is financially struggling or perhaps we don't know them as the media potray them. If Xavi is aware of yhe club financial situation, no way they are going to allow him signed Lewandowski and be earning such amount. He was in his prime in Bayern Munich and a great striker but there are other options available for them to look into but yet he went for that and currently earning highest money in that club.
Currently Chelsea are in advanced talks with Enzo Maresca the coach who led Leicester City back the premier league again. From his Tactics being analyzed and Leicester City’s current style of play i think he is good tactically and should be able to manage these Chelsea youngsters properly.
Maresca was able to brought Leicester City from the sham manager that made them relegated but you think Leicester will come this far to sell Maresca to Chelsea, if they sell him for Chelsea even at expensive price, who will help them maintain the Premier League tournament. It's better he stick to what he knows than been drag in the mud by Chelsea fans.