It was a truly horrific injury - burst blood vessels, several ligaments torn and a massively swollen knee. Colin came back (god knows how) with limited movement and played at full back. From what I've read, even with today's medical technology, there would be no guarantee of proper ligament repairs - the damage was so bad. Colin never believed that Martin Buchan deliberately set out to harm him, but Buchan never got in touch with him to see how he was - something that hurt him.
How good was Colin ? Box-to-box - used to run further than any other player in the league, but he had rapid pace as well. Think of the Yaya surge, now think of a smaller version of him making that surge numerous times in every game. Supremely skilled, good in the air and with a shot as powerful as the Peter Lorimers of the league. With a tiny number of exceptions, hardly any players of the 60s and 70s would be suited to today's game - good players yes, but generally not as athletic as they are now despite extensive training. If we could travel in time and relocate Colin to today's Prem, he would be equally as good. Like Martin Peters (the late arriving/ghost into the box midfielder from 66), he was ahead of his time. He would be as vital to the current City team as he was in the 60s and 70s.
I saw him play for a City Legends V ICI over 35s team twenty-odd years ago close up. The King would have been in his late 40s at the time. He was pinging the ball 40, 50 and 60 yards to Peter Barnes with unbelievable consistent accuracy without being able to flex his knee properly. Generally, a shy bloke who shunned the limelight.