HOUSTON - AUGUST 28: Wide receiver Andre Johnson #80 of the Houston Texans is tackled by cornerback Jamar Wall #30 and Mike Jenkins #21 of the Dallas Cowboys in the second quarter in a preseason game at Reliant Stadium on August 28, 2010 in Houston, Texas. (Photo by Bob Levey/Getty Images)
Brown would have been assigned to keep Cowboys linebacker DeMarcus Ware in check, but it now appears backup Rashad Butler will get that task.
Sources told FOX 26 in Houston that Brown inadvertently took a supplement that contained a substance banned by the NFL.
Brown was the Texans' first round pick, 26th overall, in the 2008 NFL Draft.