http://blogs.buffalobills.com/2015/08/09/why-bills-kept-thing-vanilla-in-scrimmage/
There wasn’t a whole lot of flashy plays in Saturday night’s blue-white scrimmage, but there were some big plays. Buffalo’s offense and defense were not going to lay their playbook plans for the regular season out there for a reason. As head coach Rex Ryan knows there are spies out there.
“Our guys were putting in plays, but our fans aren’t the only ones watching these things so again I think that’s something of note as well,” said Ryan. “We know there’s other teams here and so we play pretty vanilla.”
For scrimmage sessions and sometimes for just regular practice it’s not uncommon for other NFL clubs to dispatch scouts to other team’s training camps to observe what their plans might be for the regular season, especially within the division.