Umaga quit international rugby at the start of the year and Ma'a Nonu, who has 11 caps and has excelled for the Hurricanes in the Super 14, is set to come in as Umaga's replacement for the first Test against the Irish in Hamilton on Saturday.
"One guy going out gives someone else a chance," said O'Driscoll, who had some notorious battles with Umaga over the years.
The All Black was accused of delivering a dangerous spear-tackle which dislocated the Ireland talisman's shoulder on the 2005 British & Irish Lions tour.
"I'm sure he (Nonu) will be given his opportunity to go out and play similarly to what he did in the Super 14," O'Driscoll said.
Aaron Mauger will partner Nonu in midfield and will no doubt provide his usual dexterity and guile from the number 12 position.
O'Driscoll is more than aware of the danger Mauger poses.
"He seems to have been around for a long time," the Ireland skipper added.
"He's always been on the fringes of the side and he was heavily involved in beating us in 2002 when creating a couple of tries.
"But you could put out five different sets of centres in New Zealand and they would do the job. We'll have our work cut out, but hopefully they will too."