Stokes was left out of the squad at The Oval after he and seamer Gus Atkinson breached a midnight curfew following the series opener at Lord's, with an incident involving Saracens rugby player Totoa Auvaa attracting an internal investigation by the England and Wales Cricket Board.
There were suggestions that Stokes would resign or even retire in the immediate aftermath but, with no public reaction from the 35-year-old as it stands, McCullum repeatedly focused on Stokes' welfare.
Speaking on Monday, a sombre McCullum said his duty of care came before disciplinary matters or the viability of Stokes' reign as skipper continuing.
"When I first found out about it I was slightly bewildered, if I'm being honest. Then you go through a range of emotions. You go from being bewildered, on to angry, on to gutted," he said of the episode at a Chelsea nightspot.
"But very quickly … my overall emotion turned to worry and concern for Ben in particular. Since then it has been about how we support these guys, whilst not overlooking the fact they have not lived up to the standards we have set for ourselves.
"For me it's very much about how we support these guys through the next stage, in particular Ben. That is very much where my mind is at, my worry for him.
"What will be will be down the line. Those decisions are not for now. The concern is making sure Ben is fine. We need to make sure we look after him, rally around him, and in time we'll get on to those sorts of decisions.
"For me I'm just making sure I'm checking in with him. That's where things sit at the moment."
Asked if he was encouraged by Stokes' appearance in training with Durham over recent days, and the word that he is ready to play for the county against Northamptonshire on Friday, McCullum took a deep breath and a seven-second pause.
"I'm worried about Ben. That's it," he said. "I'll leave it at that."
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