Ryder was placed in an induced coma after being admitted to hospital on Wednesday morning having suffered multiple injuries including a fractured skull. Ryder was involved in an altercation with up to three people in the suburb of Merivale, Christchurch. He was then assaulted by one of the group who followed him towards a nearby McDonald's car park, police said.
O'Brien was updated with Ryder's latest condition by New Zealand Cricket Players' Association (NZCPA) chief executive Heath Mills, who travelled to Christchurch along with New Zealand Cricket chief executive David White, Peter Clinton from Cricket Wellington and Ryder's manager Aaron Klee. "He's still the same," O'Brien told BBC Radio 5 Live.
"He's in the induced coma and they tend to keep them in that state for anything up to a couple of weeks depending on the brain swelling. You have to keep them as still and as quiet as possible.
"There's no brain damage, from early reports, which is great news, so in terms of a recovery, in terms of the kind of person he'll be afterwards, fingers crossed he comes out as as similar-natured bloke."
Ryder, whose career has been plagued by off-field incidents, is on an indefinite break from international cricket and has not played for New Zealand since February last year. He has admitted in the past that alcohol has contributed to his off-field problems and it was confirmed that he was drinking with his Wellington team-mates in the bar before he was attacked.
"He's the kind of guy that always will have a drink," O'Brien added. "When he is off the stuff he's a wonderful, wonderful man - he's one of the funniest guys and very jovial - but on the other side of it, when he has been drinking he can certainly suffer the lows."
Details of the assault on Ryder were made public in a police press conference overnight. Detective senior sergeant Brian Archer said: "The hospital advise that Jesse is in a critical condition. He is in an induced coma as a result of suffering multiple injuries.
"It was an initial incident involving at least two to three people. As Jesse has gone towards the car park at McDonald's he's been followed by two of the three people, we believe, and one of those two has assaulted Jesse. It appears Jesse has been the victim of a serious assault and has suffered head injuries as a result."
Archer said he expected to have "reasonable footage" of the people available from CCTV cameras. Archer said there were "at least 10 or more witnesses" and while the people involved had not been identified there were "positive lines of inquiry".