Vio has moved to Leeds United as set piece coach.
The Italian arrives with a big reputation, having previously worked at AC Milan, Fiorentina and Brentford.
But it was not Christiansen - on whom pressure is increasing after five league defeats out of six - who put forward Vio's name.
"He’s a specialist and he’s one of the best in the world," said the Dane, as quoted by the Yorkshire Evening Post. "His CV and all the numbers tell good things about him, what he has achieved in many clubs. One of them is Fiorentina where he did a fantastic job. He has many interesting ideas.
"The club told me there was a possibility (of recruiting Vio) and of course I want to have the best with me. I’m more than happy with that."
Aston Villa's win at Preston on Wednesday saw Leeds drop out of the Championship's top six, little more than a month after they went top of the division.
And the Whites face a difficult trip to Brentford - resurgent after seven games unbeaten - on Saturday, before a two-week break for internationals.
The perfect opportunity, perhaps, for Vio to implement his ideas on the training pitch.
Can Leeds turn things around under Christiansen?