Galatasaray's defense is giving alarm

Galatasaray has a lot of good and experienced players.I think thier offens power is the best in the league but their defens is very bad.When you look at he players in the defens you see good players.Meira is in the Portugal team.Servet,Hakan Balta and Volkan Yaman played in the European Cup with Turkey.I think the problem is in midfield.Galatasaray hasn't got a good sweeper defens.Linderoth is good at ther but he has a lot of problems that blocks him to play football.Some people say that Ayhan can does this job but I don't se him enough at that position.There is Mehmet Topal but he is disabled to play too.If Ayhan and Mehmet play together in the match you can see the difference in the midfield.They help defens and don't give permission to other team to pass the ball very easily.I think Mehmet has to be good quickly or Galatasaray has to buy a good player for that position.