Ryder, who has been kept out of the national side due to multiple off-field incidents, smashed 136 off just 57 balls for Otago against an Ireland side on Thursday.
But McCullum told reporters after New Zealand' 72-run loss to South Africa on Friday that there were no plans to fast-track the 30-year-old back into the team unless everyone was convinced he was ready.
"I've already said we won't compromise the environment because we represent our country and there's certain obligations which you need to uphold out of respect to the people who support this team," McCullum told reporters.
"Jesse knows he's got some work to do, he's an undoubted talent and if he can get himself right and he's scoring runs and a vacancy is there and the group's ready for him, I see no reason why he can't come back.
"But until that happens we'd be trying to push something that is not quite ready."
Ryder last played for New Zealand during their One-Day series win over India in January.
He has not been considered for selection since he was disciplined for drinking alcohol the night before a test match against the same opponents.
"We've got to make sure Jesse is really desperate to play for New Zealand and make sure he fits within the group," McCullum added.
"He is well aware of that. Let's hope he is desperate to come back and the environment is ready for him."
(Writing by Sudipto Ganguly in Mumbai; editing by Julian Linden)
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