"I signed on loan with West Ham only to the first of January, with an option to continue, but I got injured in November," the 32-year-old told chelseafc.com.
"I did my best to come back and I started to train slowly here at Chelsea. We decided I would stay here and try to help when I can and be part of the squad, and I am happy to be here.
"Hopefully now there is the chance for me. It is a big squad, a lot of quality, but I will do my best and hopefully it will be enough.
"My fitness is much better now. I trained a few weeks with the team and the first time I played was in the last game for 15 minutes. Slowly I will feel the fitness come and I will feel much better."