Can my new iPhone 5 be replaced without Apple Care if there's a defect?

I recently got my iPhone 5 roughly two months ago. I have never dropped my phone, and recently, I noticed that my sleep/power button is becoming weaker and weaker. It seems as if the button is slanted and only the left half of the button manages to work. The right half of the button is useless now. If I don't have apple care, can my phone be replaced as a defect?

Yes. You can replace it with an identical iPhone 5. You either have to take it to the Apple store or you can send it in to them. But I think there might be a fee.

I believe so but did you order it from apple.com or buy it from a apple store (not best buy or any other stores)? If yes then you probably have a 1 year warranty. Check the iPhone 5 box your phone came in to see the warranty form thing, you should have a 1 year warranty if you bought the phone directly from apple