Jacksonville Jaguars wide receiver Justin Blackmon's up-and-down rookie season ended on a positive note with a strong statistical finish. His second season is starting off on a huge down note. The NFL announced Tuesday that Blackmon has been suspended without pay for the team's first four games of the 2013 regular season for violating the NFL Policy and Program for Substances of Abuse. Blackmon will be eligible to return to the Jaguars' active roster on Monday, Sept. 30, following the team's Sept. 29 game against the Indianapolis Colts. "I've made a mistake and I have no excuse," Blackmon said in a statement released by the Jaguars. "I am truly sorry and disappointed in myself for putting the Jaguars in this situation, and I look forward to putting this behind me and maturing and growing as a person." The news is a significant blow to a moribund Jaguars offense that is trying to find new life under coach Gus Bradley. Without Blackmon in the mix, the team's top receivers are Cecil Shorts, Mohamed Massaquoi, Jordan Shipley and rookie Ace Sanders. Perhaps the team will use fifth-round draft pick Denard Robinson at receiver as well. Quarterbacks Blaine Gabbert and Chad Henne aren't exactly playing with a stacked deck.