A simplified sterile contamination prevention bag assembly and method for reducing deployment steps is provided for covering a medical instrument deployable from a system having a deployment port for deploying the instrument from a non-deployed position to a deployed position through the deployment port and externally distal from the deployment port. The bag assembly includes a bag including a deployment port attaching end configured to be attached to a mating portion of the deployment port and a distal deployment end having a distal mating feature configured to receive a distal portion of the medical instrument. The bag is folded in a non-deployed state, and unfolded when the medical instrument is moved from the non-deployed position to the deployed position.
