Celtic have had a very good start to their season so far and they will be looking to do well in the Champions League group stages later this month.
Although Brendan Rodgers has done well to add to his squad during the summer transfer window, his defence could certainly use another addition.
Since the August deadline has now passed, the Scottish champions could look into the free transfer market to improve their options. One such option is the Swiss international Reto Ziegler.
The defender was linked with a move to Celtic earlier this summer and he could be a useful option for the Hoops.