In 1977, McGrain won his second league and cup double. He was also voted Player of the Year by the Scottish Football Writers' Association. McGrain became captain of Celtic at the start of season 1977-78 in the wake of Kenny Dalglish's departure to Liverpool. However, a troublesome foot injury that medical staff struggled to identify or treat adequately saw McGrain miss most of the season with Celtic. He also missed the 1978 World Cup for Scotland. Celtic finished the season trophy-less and failed to qualify for European competition for the first time since the early 1960s. McGrain eventually recovered from his mystery foot injury and after a tentative re-introduction into the Celtic team, now managed by Billy McNeill, played in the club's last 18 league fixtures of the season in the spring of 1979. On his return from injury, a change in his style of play was apparent. There was a noticeable reduction of pace, which in turn was compensated for by a greater reliance on anticipation of play and distribution of the ball. McGrain went on to pick up his fourth league championship medal at the end of that season as Celtic clinched the title with a dramatic 4–2 win over Rangers in their final game of the season.