The action was taken due to a violation of the league's substance abuse program. He will not be eligible to rejoin the Jaguars until the 2014 campaign and he must apply for reinstatement prior to the season.
A statement released by the Jaguars said the team would make a decision concerning his status "once he has successfully met the criteria to be considered for reinstatement to the league."
Blackmon, 23, missed the first four games of this season due to his second substance abuse violation. He caught 29 passes for 415 yards this year even though he missed those four games.
"All of us who are a part of the Jaguars family care very deeply about Justin and his well-being," General Manager David Caldwell said in the team's statement.
"That said, he must be held accountable and accept the consequences announced today by the NFL. His suspension will provide him the opportunity to receive the attention and professional treatment necessary to overcome his challenges, and we will support him during this time."
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