Christie joined Derby at the start of 2014, and his first campaign at the club was rather indifferent.
The Republic of Ireland international started well, but as Derby began to slide down the standings towards the back end of last campaign, his own form suffered.
Christie then found himself out of the team when Paul Clement took charge, but he has come back into contention recently.
Christie has played in the Rams last 29 league matches, and the defender is happy with his form.
“Obviously, a lot of people doubted it and put a question mark over me and whether or not I could step up and defend,” he said.
"At times last season, I proved that and then I went off the ball towards the end of the season.
"I think this season, I have been consistent and I think I have proved what a good player I am."
Christie has played a part in a Derby defence which has been tough to break down so far this campaign.
Only three teams in the second tier have better defensive records the Rams, who have let in just 30 goals in 34 matches.
It is at the other end where Derby have had more problems, though, and their inability to score with enough frequency has seen them fall away from the automatic promotion fight.
Derby looked like one of the front runners to be promoted from the Championship, but a run of two wins in nine matches has seen them drop down to fifth place.