The veteran centre-back faces a fight to make the starting line-up with Nemanja Vidic and Jonny Evans also pushing hard for a slot.
"When you are at a place like this, you always need competition for places," he added. "If there was no competition for places we wouldn't be as successful as we are. We have to make it difficult for the manager to pick a first XI and then we go from there. You just hope you are in the team that plays."
Rio was speaking to Talksport, PA Sport and ManUtd.com.