Orphan Other Rat?

Question
Earlier today(about 8 hours ago), I found an orphan rodent and I've now determined it to be a rat.  Judging by information I've found, it seems to be between 10-14 days old.  Its eyes are closed and its movement is wobbly (both of which are apparently normal)  I have no large questions for its care, thanks entirely to this site, save for one.
At what point, if at all, can I introduce this rat to my pet fancy rat?  My current pet rat is female and roughly 1 and a half years old.  She has never had a litter, so I'm not sure if it should be too soon.

I know that if the orphan ends up being a mouse that the two should not be put together, but I'm not sure about the other alternative.

The orphan is about 3 inches long, fuzzy, and active.  I've fed it coffee creamer, but will be getting proper food asap.  I'm currently at work, so...yeah.

Thanks

Answer
Hi there, The big problem is that if the orphaned rodent you found was wild and you introduce it to your fancy rat it could pass on a horrible disease or parasites that could kill your fancy rat. Wild rodents can harbour parasites and may be carriers of disease and show no clinical signs as they are a lot hardier than fancy rats who have had a lot of selective breeding to make them domesticated. This selective breeding decreases the gene pool and can make their immume systems weaker. I wouldn't advise mixing the two at all and if you want to keep the orphaned rodent then I would just keep it seperate and always wash your hands after handling it so that you don't spread disease to your fancy rat. Of course I'm just assuming that its wild because you found it. If you mixed a wild rat and a fancy rat and they bred you would end up with weird hybrids and its hard to tell what way they would turn out so that's another reason why they shouldn't be mixed. Since your rat is 1 and a half, this is quite old for a female rat and any chance or new introductions could stress her out which isn't really fair and wouldn't be very good for her. I hope this helps, if you have any more questions just ask.