if Marx's argument that the 'realm of freedom' is the proper telos of the 'realm of necessity' has merit, then play would seem an endeavor - among others - for realizing the former (which according to M, a shorter working day is a prerequisite)...see _Capital_ Vol. 3, p. 820, Int'l Pub.
Marx's critique of the 'working day' includes passage about workers having no time:
'for eduction,for intellectual development, for the fulfilling of social functions and for social intercourse, for the free play of bodily and mental activity, even the rest time of Sunday (and that in a country of Sabbatarians'...see _Capital Vol. 1, p. 264, Int'l Pub.
Michael Walzer briefly discusses Marx and leisure in _Spheres of Justice_, pp. 186-189 Michael Hoover