The United captain is out for two months after undergoing knee surgery.
"The disappointing thing has not been getting the stability in the defence but again that is testament to our squad. We have players who can come in and perform," said Rio.
"We have had to deal with a lot of defensive changes for the last couple of years and we are getting used to it now. But it would help if we could get some consistency with players playing week in, week out. It is the bedrock for success. But we got within one kick of winning the league last season having to deal with that, so fingers crossed with the experience we have gained having to do that we should be in good stead."