By the mid 1970s, McGrain was considered by many to be one of the best full-backs in the world. He played as what is known today as an attacking full-back and contributed significantly in both attacking moves as well as in defence. His abilities included a burst of speed, skill and control on the ball, vision and anticipation and, when required, a strong but fair sliding tackle. He won a further league championship title and a Scottish Cup in 1974 and played in the World Cup for Scotland that same year. However, McGrain was diagnosed with diabetes immediately after the World Cup, but with the benefit of medication and a controlled diet and lifestyle, continued to play without adverse effect.