I differ from your view. Dropping catches is not unusual in international matches, even great wicket keepers or even good fielders have dropped catches. I can name a lot.
Isn't fit to tie PP's shoe laces? hmm...If you remember Partiv Patel was most criticized for his Wicket Keeping and dropped so many catches during the India Vs Australia series. He was finally dropped and asked to improve his keeping.
If you dont like Karthik, it's fine but its unnecessary to critize a sportsperson so low. Yes, he dropped the catch but he is one of the best athletic fielder/wicket keeper we have in India.
