Any idea what happens with Tottenham's line-up when Modric will be back?
Kranjcar is having a very good form and Tottenham are doing solid enough even without Luka. But Modric is still, imo, their best midfielder and a place for him will have to be found. If Modric, Kranjcar, Lennon etc fit well together then Tottenham will be even stronger than they're now and they'll be serious contenders for the 4th place.
But is there a weak link in Tottenham right now that will be replaced by Modric?
You're right Tottenham are doing very well. Lennon is one of their best players this season, Kranjcar has been playing very well lately and has struck a good understanding with Defoe and Crouch. Redknapp has always been reluctant to try out Modric in central midfield.
Despite all that, i think Modric is still a guaranteed starter, because like you said he is their best midfielder. It showed when he first got injured and they started struggling very much and lost their spot in the top 4 that they had when Modric was around. Kranjcar's good form has made people forget how important Modric was to them.
There is 2 ways this could go.
Either Modric will be given a go at CM, he will probably take Huddlestones place in that case and play alongside Palacios. But Redknapp might not be willing to take that risk as Palacios and Huddlestone have been very good together. Plus, Huddlestone gives them that much needed steel in midfield while Modric is percieved as a bit lightweight for that role in the EPL.
Or Modric will be rotated with Kranjcar and depending on form, one of them will start.
There is another 3rd possibility, though this is an unlikely one. Redknapp may change to a 4-2-3-1 formation with Modric playing behind the lone striker who will most likely be Defoe. An unlikely option though as i doubt Harry will want to change a tactical setup that has been working for them, also Harry loves the big man-small man striker partnership. Crouch has been useful for them too and he and Defoe work very well together ever since both of them were playing for Pompey, ironically under Harry too.
Serie A is closer
Quality of the top 7 in the EPL is higher though. At least this season.