Defensive end Cameron Heyward, one of the leaders of a Pittsburgh Steelers defense that has been struggling this year, will miss the rest of the season with a pectoral injury.

Heyward announced the news on his Instagram account Tuesday after suffering the injury in Sunday's loss to the Cowboys and then reportedly undergoing two evaluations.

I would like to thank everyone who has been in my corner this season. It pains me to say that I will not get to continue playing this season. My role will change as I can not play but it will not change the goals the team has set out. My support for this team will only grow and I look forward in watching this team grow and fight on. Hate being on the sideline but there is a greater plan taking place. My patience will be tested but I look forward to 2017. My hand will remain in the pile no matter what!

A photo posted by Cam Heyward (@camhey97) on

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The 4-5 Steelers rank 25th in the league in yards allowed per game, and have lost four straight. Heyward has three sacks this season after posting seven last year and 7.5 in 2014. He was the 31st overall pick in the 2011 draft and has been a starter since the 2013 season.