"I was frustrated more last season as I've ever been because of all of those injuries," Charles told ESPN.com's Adam Teicher on Tuesday. "I was frustrated because I didn't feel my body was right the whole season. But I battled through that time. That's all I could do. I felt like I was in a fight and I had to respond. I had 12 weeks to finish the season, and it felt to me like I had 12 rounds to go.''