Leeds United were beaten 4-1 by Wolverhampton Wanderers last night.
Vieira was sent off for Leeds last night, and the youngster’s dismissal changed the game.
Leeds had managed to pull a goal back and were on the front foot, when Vieira was given his marching orders.
The Whites’ task was tough enough with 11, but made even harder with 10.
And Wolves ended up going to to win 4-1 in front of their own supporters.
Leeds were outplayed from the moment which Vieira was sent off, but Christiansen was happy to take the blame for the red card.
He said: “He has to learn from that. I have to learn from that. Perhaps I should have changed him. I have to take my responsibility also.”
Leeds’ defeat to Wolves leaves them in 10th place in the Championship table, and they are now 15 points behind Nuno’s side.
Leeds are next in action at the weekend, when they take on Barnsley at Oakwell, and they will be eager to get back to winning ways in the Yorkshire derby.