Grimes was an undrafted free agent out of Notre Dame after this past draft. He had a hamstring pull during the rookie mini-camp, which was probably his downfall. Joel said back in June about Grimes' injury, "Certainly not a good thing for someone like Grimes to be hurt during this time."
Presumably, that's what did Grimes in. A lack of evaluation time for the Kansas City Chiefs coaches. Even though Charlie Weis coached him at Notre Dame, if you can't get on the field it's tough to stay on the team. Josh Looney also tweeted this morning that Grimes had a tough time holding on to the ball when he was playing.
WR Verran Tucker isn't anybody special, just part of this natural reshuffling of the 5-10 guys at the bottom of each NFL team's roster each offseason. He played at Cal and was initially signed after the draft by Dallas as an undrafted free agent.
Expect more of these signings and don't put too much thought into them. They're camp fodder. For my full thoughts, I refer you to my very well received post from 2009 titled Don't Sweat These No-Name Free Agent Signings by the Chiefs.
H/T to RodeChief for the link and to NJ Chiefs Fan for getting it to the front page.