From Longman Dictionary of Contemporary Englishon the sidelineson the sidelinesTAKE PART/BE INVOLVEDnot taking part in an activity even though you want to or should dostand/stay/remain etc on the sidelines You can’t stay on the sidelines for ever; it’s time you got involved. → sideline
Examples from the Corpus
on the sidelines• Only McManaman, with a serious knee injury, will still be on the sidelines when they return to Villa Park tonight.• And I see companions and conviviality as much more on the sidelines of life than at the centre.• And Congress, with its hands in its pocket-wherein reside its true concern-stands mute1y on the sidelines.• How can we sit on the sidelines when thousands of innocent civilians are being killed.• Jody is standing on the sidelines watching the visitors go through their drills.• Tom stood on the sidelines , cheering his teammates.• You can't just wait on the sidelines and hope things will improve.• A bad tendon strain in Aldaniti's off-foreleg had to be fired, and he was on the sidelines for eighteen months. 