The latter has recently emerged from the Blues youth setup and into the first team.
Now Rudiger, who is a recent learner of English, is having a hard time understanding what the young Scotsman is saying during training.
"The last word I learned? There is a lot but the last one was rapid.
"For me, you say the guy is quick but Danny Drinkwater said to me 'this guy is rapid' and I didn't know what that meant. I made sense when I thought about it but I never had it in my vocabulary before."