The Kansas City Chiefs had a number of tryouts recently, including a former track and field star from England. According to Aaron Wilson, the Chiefs hosted DE Lawrence Okoye, DT Derrick Lott and RB Gus Johnson.
Okoye is the headliner here and not just because the Chiefs have had success with that name before. He is a former track and field star who competed in the 2012 Summer Olympics. He entered the 2013 draft despite never having played American football. The 49ers ended up signing him after the draft and he stuck there for a couple of years. Our 49ers blog has a nice writeup on him from this preseason.
The other two players I'm not as familiar with. Here's what their NFL.com draft profiles say. Click the link for more info.
DT Derrick Lott: Skilled pass rusher who understands the position and was simply too athletic and too talented for most of the competition he faced while at Tennessee-Chattanooga. Is a natural fit as a three-technique in a 4-3 defense, but could garner consideration as a 3-4 defensive end if he can prove he's strong enough.
RB Gus Johnson: Compact running back with power in his lower body to break tackles and extend runs, but he's not a chain-moving power runner with a desire to punish tacklers. Tape shows borderline athletic ability as a pro with little to no value as a third-down back, which limits his draft value.