Chelsea's Michael Essien may sacrifice playing for Ghana at the World Cup for the sake of the rest of his career.Essien, 27, has not played for Chelsea since tearing a hamstring in December. He then hurt his knee on Ghana duty at the Africa Cup of Nations in January. "If I make it for the World Cup then great - if not I have my whole career ahead of me," he told Chelsea's official website."The last thing I want is to rush back and cause more problems down the line." Essien's last run-out in a Chelsea shirt was against Apoel Nicosia in the Champions League in December.Having recovered from his hamstring tear, he then hurt his knee at the Africa Cup of Nations, but that was only expected to keep him out for six weeks.It was anticipated he would make his Chelsea comeback in the Champions League game against Inter Milan, but his knee continued to swell up and he underwent four lots of surgery inside a fortnight.Essien is central to Ghana's hopes in South Africa, but with Ghana's first game against Serbia on 13 June, he has admitted that he might be forced to look on as a spectator. "The World Cup is the best and most difficult football tournament in the world and I would rather be there fully fit," he said on his official website."We will just have to wait and see. If not I'll have to sit at home and support the team like every Ghanaian."Source: BBC