Player on the floor

[LepTalBldgs]

The game I was watching which brought up this question was college, but it was local and not televised.

I am still searching for how to apply this situation to High School rules.

Situation: Action under the boards, offensive player falls to floor and defensive player secures rebound and trips over player on the floor causing ball to come loose.

Does player on the floor have a legal guarding position or is this a block?