Hernández umpired in the World Series in 2002 and 2005, as well as the All-Star Game in 1999, 2009, and 2017. He has officiated in seven League Championship Series (2000, 2001, 2003, 2004, 2007, 2010, 2016), and in eleven League Division Series (1997, 1998, 2002, 2005, 2009, 2011, 2012, 2015, 2017, 2018, 2020). Hernández also worked Game 7 of the 2008 ALCS as an injury fill-in for Derryl Cousins. For the second half of the 2011 baseball season, Hernández was moved from the umpiring crew of Joe West to the crew of Gerry Davis.