It is the iconic imagine of the Eagles' 2011 training camp. Included in the 1,000 words said by the photograph of defensive coordinator Juan Castillo headbutting helmeted second-year linebacker Keenan Clayton would be intensity, dedication, sacrifice and, well, ouch.

Much has been made of Castillo's fiery nature as the new steward of the Eagles defense, but what of the impact on the recipient of the infamous headbutt? Clayton and Castillo's meeting of the minds took place during the morning practice on August 1. It didn't take long for Clayton to start hearing about it.

"It actually hit twitter the same day. Before I got back to my room everybody was texting me and calling me, saying, 'What did you do now?'" said Clayton, who added that he does have a copy of the picture. "For the record, I was not in trouble, Juan was not yelling at me. He was just showing us to keep our head up and use our face on contact instead of dropping our heads.

"If he's going to headbutt me with my helmet on, he had nothing on, yeah, it let me know if he could do it and he's (51 years old) with no helmet, I can use my face with a helmet."

While Castillo's passion was exhibited in the clash with Clayton, it was on display throughout training camp. After what seemed like every play, Castillo would charge in from the sidelines, yelling and slapping players on the back as if every play were a fourth down in the Super Bowl. That kind of atmosphere was welcomed with open arms by Clayton, who has admitted in the past that he struggles to practice as well as he plays on game day.

"To a certain point, you feel like you need to match his intensity," said Clayton. "If he's going to be high-strung and have a lot of energy, it kind of just brings energy to everybody else. Sometimes you're just like 'Come on, Juan, calm down.' But at the end of the day ... what if he were just over there being quiet? Then we probably wouldn't have had any energy at all."

Clayton finds himself as the nominal fourth linebacker at the moment, with Jamar Chaney, Casey Matthews and Moise Fokou currently sitting as the three starting linebackers. But Clayton is considered to be perhaps the best of the team's linebackers in coverage and has worked with the first-team nickel defense, so he should see plenty of the field in his second season.

And when he finds himself facing a ball-carrier with a chance to make a tackle, one thing's for sure - Clayton will keep his head up.