His credits include The 4400 (2004–2007), Taken (2002), V (2009–2011), Friends (1995), Saved by the Bell: The New Class (1994), JAG (1999), Silk Stalkings, CSI: Miami, CSI: NY, Burn Notice, NCIS, Law & Order: Criminal Intent, Journeyman, The Legend of Bagger Vance (2000), Minority Report (2002), The Emperor's Club (2002), National Treasure: Book of Secrets (2007), The Vampire Diaries (2016–2017), and All Rise (2020).

[3] He started his television work in the early 1990s, appearing in episodes of Married... with Children,[3] Melrose Place, Friends and Saved by the Bell: The New Class.

[3] Gretsch has also had supporting roles in a number of films including playing Bobby Jones in The Legend of Bagger Vance (2000),[4] Minority Report (2002),[4] The Emperor's Club (2002) and National Treasure: Book of Secrets (2007).

[4] In 2008, Gretsch had a recurring role as Pete Raynor, Lindsay Boxer's love interest, on the television series Women's Murder Club.

[4] Some of his notable roles include Tom Baldwin on the USA Network series The 4400 in which he starred alongside actress Jacqueline McKenzie,[4] and as Owen Crawford in Steven Spielberg's 2002 science fiction miniseries Taken.