I'm not sure which players you're referring to, Terrell Davis is the one that seems to be talked about in this thread, and Eli Manning is the one Deion mentions in the linked article.
Davis was the best running back in the NFL for several years and a Super Bowl MVP. That's not mediocre.
Manning won 2 Super Bowls, was Mr. Clutch against one of the greatest dynasties in NFL history. Definitely not the best QB in the league each year, but not mediocre.
Define "several." TD only had 3 good seasons and was seamlessly replaced by Olandis Gary. He shouldn't sniff the HoF.
Eli is a career .500 quarterback who always ranked near the middle of the league in passer rating - only had 1 top-10 performance. He is entirely mediocre, and skews more towards bad than good. He's what, the 15th-best quarterback of his era? Off the top of my head...Brady, Peyton, Brees, Rodgers, Romo, Rivers, Roethlisberger, Warner, Palmer, Ryan, Stafford, McNabb, Newton. Even Mike Vick had a passer rating of 86.5 in 2013 at 33 years old. Eli only surpassed that number 6 times in his career, and his average was lower lol.
I mean should Joe Flacco be in? He actually played good in their playoff run.