Ravens C Matt Birk (varicose vein surgery) participated in Baltimore's first training camp session Tuesday. "I feel better," Birk said. "(The doctors) say it'll help me feel better during the season. My leg won't get as fatigued. So it's a good thing." Birk has dealt with multiple injuries the past few seasons, but hasn't missed a game since 2005. He graded out as Pro Football Focus' No. 8 center in 2011.