Fox Sports reported that "more than 10" players failed drug tests at the combine, and the biggest names on the list are LSU quarterback Zach Mettenberger and Florida State defensive tackle Timmy Jernigan.
The drug use itself might not be the biggest red flag, depending on what the drug was. Miami offensive tackle Seantrel Henderson, for example, reportedly tested positive for marijuana, the same drug that commissioner Roger Goodell wouldn't rule out letting players use for medical reasons. In 2014, when two states have legalized marijuana, you'd have to be pretty conservative to overreact to someone using it.
See this story on sports.yahoo.com