As with Tottenham's Paul Konchesky, on loan from Charlton, it was expected that he would be cup tied, but Steve McLaren at Middlesbrough has had a change of heart allowing him to be cup tied.
"I know Robbie well from Scotland and he does well getting up and down that right hand side so he will be a good addition for us," says Christian.
"He is a good player and a good lad who works really hard.
"He will take the ball all day, attack down the line and defend when he has got to, and plays the right back position really well."
Christian can't wait to get stuck in to Spurs and adds:
"I am really looking forward to it and I was saying to the boys it is an exciting game playing against a Premiership team again and especially with it being Tottenham.
"The only motivation we need is that it is against Tottenham and we want to get into the next round."
Hayden Mullins is still cup tied, having played in the competition for Crystal Palace, and he is still recovering from a dead leg which forced him out at half time against Cardiff.
"It is a shame for Hayden getting injured on Saturday when he was doing really well, and his debut was good at right back against Forest.
"Hopefully Hayden won't be out too long and the same goes for David Connolly who was looking really sharp at Cardiff and causing them a few problems before he went off.
"I think you miss guys of that quality."
Looking at the Cardiff game, he adds:
"It could have been three points I suppose; normally you would be quite happy with a point there but in a way it was a little bit disappointing because we have had three draws at home before that.
"We just have to make sure we win at Coventry on Saturday.
"I don't know what happened there but if it was offside, so be it; I thought we defended well most of the time but we needed to create more chances, which we are capable of doing, and hopefully against Coventry we can stick some away."