I thought he was bought in as competition for the CB's - though what you say makes some sense with timing.
Sami was quoted as saying to a journalist back home that he didn't think some of the team really understood what Rafa wanted from them in zonal marking. Cue Sami being dropped immediately, us having to suffer through some disgraceful defending and the team enduring some of the worst passing ever witnessed. I remember vividly a game against Southampton; Gerrard gave the ball to Pellegrino 2 1/2 yards away; Pellegrino tried to pass it back to him and kicked it 3 yards in front of him and straight over the side line. Gerrard's expression was priceless; it was part utter confusion, part complete disbelief but you could also see there was just the beginning of a suspicion that this guy was a double agent.
6 games we put up with him before Rafa finally pulled him out and put Sami in there after Pelle had given away a pen against someone. That said, while I'm 100% with Keni, Sami did come back looking refreshed and in fantastic form. It must have been killing him to see what the guy was doing to his team mates.