Pierzynski says he suffered an oblique strain last year that caused him to miss a few days, but this injury is worse, according to ESPN. He has hit .263/.297/.411 this season as the Rangers' starting catcher. After spending the last eight seasons with the Chicago White Sox, he signed with Texas as a free agent in the offseason.
Pierzynski's biggest impact with the Rangers so far may have come from his handling of the pitching staff. On the season, the backstop has a 2.87 catcher's ERA, the best in the MLB. The Rangers' pitching staff as a whole has the second best ERA in the major leagues.
Chirinos has not played in the majors since 2011, when he was with the Tampa Bay Rays. This is his first season in the Rangers' organization. He's been one of Triple-A Round Rock's best hitters, posting a .295/.404/.487 line through 23 games.
While Pierzynski is out, backup Geovany Soto will likely take on the starting catcher position. The 2008 NL Rookie of the Year has played in 10 games this season, posting a .570 OPS.