"He looked real good, though he probably won't admit that he's feeling good or feeling back to the way he wants to be," Decker told The Denver Post.
Decker said the session essentially was an opportunity for Manning and his teammates to begin the process of establishing chemistry.
"Just some drill work, talking through stuff, so he gets familiar with the verbage and the calls," Decker said. "The biggest thing is he wanted to get a feel for us, and a feel for being under center."
According to the NFL's collective bargaining agreement, Manning is allowed to organize workouts on his own until April 16, but the workouts cannot take place at the Broncos' team facility. Manning told The Post last week that he needed to brush up on what he is and is not permitted to do during the offseason.