Chelsea’s misfortune with injuries this season continues, as Germany captain Michael Ballack became the latest addition to a long list of players in the treatment room.

Ballack has been ruled out for at least two weeks after it was clear that the 30-year-old midfielder had damaged his hamstring in an international friendly against Switzerland. A scan showed a small hamstring tear, which could in fact sideline him for up to a month.

He will now miss Blues' Premiership meeting with the buoyant Middlesbrough at Stamford Bridge on Saturday, so also the FA Cup fifth round tie against Blackpool or Norwich City the following weekend and almost certainly the first leg of Chelsea's Champions League tie at Porto on February 21.

Ballack might just target the Carling Cup final against Arsenal on February 25.

Meanwhile, 19-year-old Nigerian midfielder Mikel John Obi is set to miss two matches with a thigh strain while left-back Wayne Bridge is also expected to miss Boro clash because of a thigh injury.

Specialist right-back Paulo Ferreira could most likely have to fill in for Bridge as manager Jose Mourinho has limited options and the first-choice Ashley Cole is also out injured.