He was like: "Huh, me?! Wow!" and then took a quick glance at his other team mates on the bench(who probably were pissed off for not being chosen). He then stood up quickly with the most confused grin on his face, just before it struck him that it might look like he was gloating. So he quickly returned to his "serious face", and started to warm up. While running up and down the sideline, I could occasionally hear him talking to himself with a low voice, saying things like: "Wow, I was chosen to play.. This is going to be awesome", just loud enough for his coach/captain to hear it. I guess it was important to still show how much he appreciated this opportunity