The on-loan striker returned to Chelsea earlier this week for treatment and having had the imflammation drained out of the knee was initially expected to be back in training with the rest of the Blues squad at Wast Hills at the end of this week.
However, Blues boss Steve Bruce has confirmed that the Finland international, who has missed Blues' last two games against Charlton and Lincoln, needs surgery on the injury because the fluid on the knee has returned and he could be sidelined for a further six weeks.
Lets hope that fellow striker Emile Heskey gets over the knock that saw him substituted in the game against Lincoln. The Blues forward worryingly limped off the St Andrew's pitch 23 minutes from the end of the Carling Cup tie against The Imps on Tuesday night.