NFL: '21 salary cap to shrivel due to COVID-19   Unknown financial implications from the coronavirus pandemic might force the NFL to reduce the 2021 salary cap by as much as 50 percent, ESPN's Adam Schefter reported.   With uncertainty around the 2020 season, including whether fans will be able to attend games at any point, and other revenue-tied variables up in the air, the NFL enters the summer months planning for the limbo that could follow next offseason.   Sche