Branislav Ivanovic expects to be out for three weeks with the hamstring injury he picked up on international duty. Ivanovic returned to London at the weekend for scans after picking up the tear in his Serbia's 2-0 win over Albania on Thursday. The absence of one of Jose Mourinho's key defensive stalwarts means left back Baba Rahman could start against Aston Villa on Saturday. That would see Cesar Azpilicueta revert to his natural role at right back in a Chelsea defence that has leaked 17 goals in the Barclays Premier League - the division's second-highest conceded total.