The Broncos were back at their Dove Valley complex Sunday for meetings as well as required work in the weight room.
Wide receiver Brandon Marshall was said to be among them and was scheduled to be on the field Tuesday for the Broncos' next practice. The players will be off today.
McDaniels said Marshall did not make the trip to Seattle because he was among the players who were "not ready and able to play in this game."
The other three — safety Brian Dawkins, wide receiver Brandon Lloyd and running back Knowshon Moreno — are injured.
Asked if players were left behind for injuries only or for other reasons, McDaniels said, "Both."
McDaniels also answered "absolutely" when asked if Marshall would be at practice Tuesday.