After graduating from the University of Delaware, he began umpiring in the minor leagues in 1982, eventually reaching the American Association before being promoted to the NL. He umpired in three World Series (2004, 2009, 2012) and in two All-Star Games (1998 and 2009). He has also umpired in the 2014 National League Wild Card Game, seven American League Championship Series (2002, 2007, 2008, 2010, 2014, 2016, 2018), and in 10 Division Series (1997, 1999, 2000, 2001, 2003, 2004, 2006, 2009, 2011, 2012).