Richardson roomed with Sam when they were teammates at the University of Missouri.
"I am (proud)," Richardson told SportsNet New York on Tuesday night, per the New York Post. "He had his best season when he came out to the team. I'm actually happy for him and it worked out for him, it didn't go the opposite way. I know he was scared and he was nervous, and being himself and him getting that monkey off his back was well worth it, because he had his best season of football at Missouri."
The Defensive Rookie of the Year said he knew Sam was gay when they roomed together at Missouri. Sam's sexuality didn't change how Richardson viewed his friend and teammate.
"Yes, I knew," he said. "Regular guy. He has his own sexuality. It didn't take nothing from him -- he was a great teammate, great person, everything you wanted out of Michael Sam, you got out of him."
Richardson believes Sam will be welcomed into whichever NFL locker room he is drafted.
"I believe (so), unless your team's immature-minded," he said. "If guys can't get past that, it's just crazy. It just might be weird at first for you if you're not used to it, but sexuality has nothing to do with him being on a football field. He's a completely different person, he puts his face on, no smiles, he's serious business. He's a killer."