Much sport psychology research has been devoted to the negative effect of anxiety on athletic performance and why some athletes who perform well in practice or no pressure situations suffer from performance anxiety when it's showtime.
Researchers have found that athletes either have a positive or negative reaction to adrenaline. The successful interpret arousal to be facilitative while some find the increase to be debilitative.
Kyle's performance issues when expectations are high and the spotlight is on go back to his days at Purdue. He was getting Heisman Trophy attention until his fumble was run back for a touchdown late in the 4th quarter against Wisconsin on national TV (sound familiar?).
I think that Kyle knows he doesn't do well when there is a bunch of adrenaline in his system and that may account for his quiet calm demeanor in the game. He's probably purposely keeping himself calm and avoiding anxiety.