KO late entry

[phansen]

Ready for play whistle has blown and K is ready for kickoff. K only has 10 players and k11 runs onto the field. He starts at about R's 35 yard line, runs past the R front line and into position on the opposite side of the field. I'm thinking he can't be offsides until he's onsides first, maybe a substitution infraction, but they only have 10. Then possibly delay, but the 25 seconds hasn't expired. So I think I have nothing as long as k gets the kick away in time. I got an earful from the coach, but I still think there was no penalty and can find no rule to say otherwise. If I'm wrong, please cite rules or case book.