The former Gers captain joined Southampton last summer in a deal reported to be in the region of £800,000.
The Northern Ireland international was one of many players forced to leave Ibrox after the club fell into administration, but he still harbours ambitions to rejoin the club later in his career.
"On the day it was announced Rangers were going into administration it was just a series of words to us until we absorbed the ramifications of what had taken place," he said
"I had just signed a new, five-year contract and it had always been my intention to honour that agreement and devote the largest part of my career to the team I considered to be one of the biggest names in world football.
"I loved the club and the fans but I had to take a decision which was best for me, my family and the remainder of my career. There was so much uncertainty, so I was delighted Southampton made an acceptable offer.
"It was the toughest decision of my life when I left for another club. I gave the team 100% every time I went out on to the park for Rangers.
"If everything goes to the plan I have in my head I'd like to come back and play for the club again before my career ends. I still follow Rangers and they continue to mean a lot to me."
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