The condition of New Zealand cricketer Jesse Ryder who was assaulted outside a Christchurch bar, is improving as police arrested two men in connection with the brutal attack.

Lifting the hopes of his family and friends, Ryder gave the thumbs up to his neurosurgeon. His manager Aaron Klee said Ryder is still in a critical state but doing a "lot better" now.

"They are assessing his coma at the moment and when the right time will be to bring him out of the coma," he said. Ryder's teammates have reassured that the cricketer has not suffered any brain damage in the attack.

Klee also praised the "phenomenal" support Ryder and his family has received from people around the world.

"We have had lots of down time sitting around and have been reading the messages of support ... We have been collating those and trying to communicate them with Jesse," Klee said.

Christchurch City Councillor Aaron Keown has organised a candlelight vigil to express support for Ryder.

Meanwhile, a 37-year-old man, one of the two involved in the attack, has been arrested, police have confirmed.

Earlier, police had arrested a 20-year-old man and charged him with assault. He was tracked down by the police with the help of a taxi company and has been released on bail.

The second man has also been charged with assault and both the accused will appear in the Christchurch District Court next Thursday, according to TVNZ.

Detective Senior Sergeant Brian Archer said that the two men arrested were related to each other.

Earlier reports had suggested that three people were involved in the attack. The police have now clarified that there were only two.

Archer said: "I've been able to review the CCTV footage and saw that a member of the public got involved to try and break up the fight and that probably swelled the numbers from what people saw, but I believe the altercation involved two people initially and one person in the second incident (outside McDonald's entrance)."

He cautioned that the case is far from over. "At the moment we have a reasonably clear picture of what has taken place. But, we don't know the full ins and outs of why this (attack) has occurred," he said.