The announcers are talking about how Youk is intense on every AB. That is an exhausting task over the course of 162 teams, and probably explains why he has better first halves than second halves. Intensity and heart has made Youk and Pedroia above average players despite their very average physical skills. Yaz was an intense player, although he was criticized for not running out grounders in his first couple of years. He had above average skills, but his work ethic and intensity made him into a star and a Hall of Famer.