What were equivalent players paid before the unions existed?
Sports unions are responsible for the massive increase in pay over the years. Those top performers would have been making much less in the absence of a union, both at the start and in the peak of their careers. I personally don't view that as decreased individual leverage.
> As soon as the union-negotiated common salary time runs out, top players’ pay jumps several times.
That 'several times' level only exists because of the unions.