Like many an aspiring performer, Valley developed an interest in acting as a high school student, but he put those ambitions on hold when was accepted at the US Military Academy at West Point. After completing his degree in mathematics, he was stationed in Germany for most of his five-year stretch in the Army, although he did see action as part of the ground forces in Operation Desert Storm. While in Berlin, Valley was spotted by an agent who convinced him to try acting. Shortly thereafter, he was cast in his first screen roles, in the thriller "The Innocent" (filmed in 1993; released in 1995), directed by John Schlesinger, and in Wim Wenders' "Faraway, So Close" (1993).
Having signed with the agent, Valley began to land small roles in German TV productions while he trained at the Etage School of Arts in Berlin. By 1991, with some stage experience on his resume, he moved back to the USA and settled in NYC where he supported himself with work in commercials. He also landed his first daytime TV role as a priest on NBC's "Another World" and then segued to primetime in the syndicated 1994 TV- movie "Vanishing Son IV". Although he was the fourth actor to portray Jack Devereaux on "Days of Our Lives" and had the unenviable task of replacing a popular actor, Valley was able to make the character his own and win over the skeptical fans, many of whom were disappointed when he left the show after his three-year contract ended.
Valley was not idle, though, so his admirers were able to see him in a small role as a resident in the HBO original "Breast Men" and as Robert Kennedy in the TNT miniseries "George Wallace" (both 1997). On the big screen, the actor appeared as the leader of an FBI tactical squad in "The Siege" (1998), was seen briefly as Rupert Everett's doctor lover in "The Next Best Thing" (2000, directed by Schlesinger) and had the title role of a gunfighter in the Western "Jericho" (2001). Valley also made guest appearances on several TV series, most notably in the 2000-01 recurring roles of Marin Hinkle's hunky love interest on ABC's "Once and Again" and as Maura Tierney's loutish ex-husband in NBC's "ER", before landing his first regular primetime gig.
In fall 2001, he was cast as Robert Greeley, the arrogant scion of a wealthy, newspaper-owning family with more than its share of skeletons in the closet, in the well-reviewed but short-lived Fox primetime serial "Pasadena" (2001). Valley also received strong critical praise for his turn as the lead in his next series, the UPN comedic crime actioner "Keen Eddie" (2003-2004), in which he played a tough, sharp-tongued, non-nonsense New York detective who finds himself assigned to a police unit in London; despite a loyal cult following, the show lasted a single season but was popular enough to merit a DVD release.
Trading the rough-edged characters he previously specialized in to play the more refined, morally centered attorney Brad Chase, Valley joined the cast of David E. Kelley's wonky lawyer drama "Boston Legal" to provide a rival and counterpoint to James Sapder's morally slippery Alan Shore.