My 6.5 pup nips at our 5 year old dog's back legs quite often when they're in the yard. Not only that, pup pounces and yanks at our adult frequently... I know it is natural for dogs to play rough but at times I worry our new pup has an attitude problem.
Know of any modifiers?
Thanks!

Just leave them alone. Your older dog will discipline the pup if he gets too boisterous, and he'll do a better job of it than you can. Adult dogs rarely have to discipline an obstreperous pup more than once or twice before they get the message.

For example, I brought home a 12 week old Dachshund pup. If you would have watched him playing with my adult Dachshund, Oli, you would have thought he was being too rough. But the old boy put up with his antics until he bit hard enough to almost break the skin. At that point, he got a "spanking". Oli yelped, pushed him down, held his little head between his jaws, and made horrible sounds. Puppy was immediately apologetic and curtailed his antics. For a few minutes. After the second "spanking", he behaved himself. Now they are the best of buddies, although the puppy still needs a gentle reminder from his big brother now and then.

Another thing to keep in mind. Not only will your older dog teach him to mind his manners, he's also teaching bite inhibition; nipping during play is OK, but don't bite HARD!

What kind of puppy is it? Vetgroomer is correct but I was wondering if it was a natural instinct such as a herding dog.

yah i think thats totally normal...

My dog was very nippy when we first brought her home. She was biting on everyone's toes. We couldn't wear open toe shoes. Puppies are teething at that age and want to bite and chew on everything in sight. The puppy will grow out of it and the adult dog will gain the alpha dog position.

________________________
Happy K-9 Dog Care: Your All-in-one Resource Guide
SitStayFetch: Effective Dog Training