Regarding Colville's final season:
Early 1949 was a period of upheaval for the Rangers. The season began with an automobile accident that sidelined four regular skaters (Buddy O'Connor, Frank Eddolls, Edgar Laprade and Billy Moe). Frank Boucher, who had already amassed one of the worst coaching records in history since taking the post several years earlier, was forced to scramble just to fill a lineup, making several trades that would affect the lineup down the road (ie, Jim Henry for Alex Kaleta and Emile Francis).
At that time, Colville was captain but also the oldest skater in the league (Turk Broda was 2.5 months older for the league title) and suffered a recurrence of an old groin injury early in the season. About a month later, with Colville still out injured, Boucher was replaced by Lynn Patrick as head coach (Boucher was of the philosophy that managers and coaches should be separate positions, and retained the manager title). At the same time, Colville accepted the AHL coaching position that Patrick had vacated. In taking that position, Colville effectively retired from the NHL and put himself on the management track -- same as Boucher had done a generation earlier.
In New Haven, Colville played only 28 games in 1.5 seasons. Without being able to verify this suspicion, it looks like he was only playing on a substitute basis. He was 5 years older than anyone else on the roster, suffering from ulceritis, and he knew as well as anyone that he had no business playing in a minor league. The stint in New Haven ended when Patrick left New York two years later, leaving the coaching position open for Colville.