I know it's not uncommon for NFL teams to try out non-football players, but I find it strange that a football team would pick such a notable player from another sport....
hi! it's possible you'll get answers here, but it would be worth x-posting to /r/football /r/nfl (oops: thanks /u/davratta!)
I read an article that touched on Walker a couple years ago but I can't find it in a Google search. The article was on "Mr. Irrelevant," the last guy picked in each draft, and it mentioned that Walker was among that fraternity. I just double-checked, and there were seventeen rounds in the 1967 draft. That's 445 picks. That being said, Wikipedia lists two undrafted pro-bowlers and two undrafted Hall of Fame inductees from that same year.
As a followup question, does anyone know if Walker used his selection as leverage at all (like Elway did with his baseball prowess)?