New Zealand Cricket tweeted "The whole NZC team's thoughts are with @DijaRyder this morning''.
Crusaders player Zac Guildford tweeted "Thoughts and prayers with @DijaRyder much love''.
Monty Betham, whose gym Ryder trained in, tweeted "Come on @DijaRyder show the fight you have within thinking of you brother.''
Hawke's Bay Basketball star Paul Henare wrote on Twitter: "Sad to hear about Jesse Ryder today. There are some seriously nasty/cowardly people out there. Hope he pulls through ok Kia Kaha brother."
Ryder's family has reportedly travelled from Hawke's Bay to Christchurch to be at his bedside.
Wellington Firebirds players were in a sombre mood at Christchurch International Airport as they flew home this morning.
Blackcap and senior squad member Grant Elliott said they were all waiting for some good news.
"It's not great, is it?'' he said.
"But we don't know how serious it is. We're not too sure what's happening - it's all pretty confidential at the hospital.
"We're all just hoping for the best.''
Elliott wouldn't say who was out with Ryder or comment any further.
Ryder was in Christchurch playing for Wellington in the major preliminary final against Canterbury at Hagley Oval yesterday, which Wellington lost by 61 runs. Ryder was dismissed for a golden duck during Wellington's unsuccessful run chase.
He had been due to depart New Zealand this week to join the Delhi Daredevils for this year's edition of the Indian Premier League where he was bought by the franchise for $USD260,000 (NZD310,577) in February's player auction.