Johnson's attorney released a statement Tuesday stating the suspension was upheld for violating the league's policy on performance-enhancing drugs.
"We are disappointed with Arbitrator James Carter's summary ruling," Steve Zashin wrote in the statement obtained by NFL Network's Mike Garafolo. "We will wait for his formal written opinion. After we review that decision, we will consider all available legal options."
Johnson was previously suspended four games for a PED violation in 2014.
The Eagles released the following statement from executive vice president of football operations Howie Roseman after the news:
The 26-year-old Johnson played in the first four games of this season while appealing the ruling that came down in early August.
Johnson has played fantastic to open the season on a very good Eagles offensive line. Perhaps one of the surprises of the season is how well the blocking has held up in front of Carson Wentz after the group struggled last year under Chip Kelly. Pro Football Focus ranks Johnson its No. 3 overall offensive tackle to start the year.
Missing Johnson until Week 16 is a massive blow for an Eagles squad in playoff positioning. How Johnson's absence affects Wentz, who has been sublime to start his rookie campaign, is something to monitor.