Yes, it was Broncos RB Montee Ball working with Peyton Manning's first-team offense.
Klis' tweet added that Ronnie Hillman was carrying around a football everywhere. Hillman had another preseason fumble leaving the door open for Ball, or even Knowshon Moreno. But it appears the team is going to try Ball. Ball had been struggling in pass protection up this point, a big no-no when Manning in your QB.