be patient!
I brought our puppy home at seven weeks to meet my two cats. I knew that if they were to get along at all, they would at least need to meet when they were close to the same size. The first few weeks was difficult, so be prepared for some incidences. The only real worry is the cat damaging tysons eyes. Any other scratch will teach tyson much needed respect for your cat.
At around 9-10 wks your pup will be at least the same size if not bigger than your cat, and starting at this point, I promise the cat will get what's coming to him.

Just kidding.
Seriously, for a few weeks you will have to fully supervise their meetings. Be sure you continue to give your cat as much, if not more attention as before. Who knows, maybe he was abandoned the first time because a new addition came into the family? You never know. BE PATIENT! You will only be scared for your puppy for a few more weeks, then you will be more worried of the pup aggravating the cat too much, or stepping on him

Really, though this problem will work itself out. Now when mine play too rough, all three of them go into time out together

pretty funny.
My ruckus is now 10 months, and when the cats arent being chased by him, they are snuggled up for a nap with their big brother. Makes for some very cute snapshots!
Good luck and take heart! Its worth it.
Rachel
Ruckus, Remi,+Romeo