Which "others"?
I wanted Terry instead of Cahill because he's a better defender. Luiz is in midfield is fine, against certain sides, but given we played 2 similar combative defenders in Ivanovic and Cahill I felt we would have matched up better against a defender that can read the game like Luiz or Terry.
Luiz has played in pretty much every game for the last 6 weeks (possibly more), he's clearly fatigued, playing him in midfield gave him a lot more running to do and it showed towards the end.