Kalou could be a good sub. But not more. To be honest, for replacements i would put Kakuta and Sturridge ahead of him, because they are the Chelsea's futur (mainly Kakuta which has the potential to be one of the best world players) and they need gain experience. Back in the days, Kalou was a good prospect... But since he was at Chelsea, he never improved. And in my opinion he will no more improve (or just a little bit). And for me, if he does not show something better this year, then we must get rid of him.