Super Bowl-winning linebacker Bryan Braman, who played for two teams across seven seasons in the NFL, has died aged 38 after a battle with a “very rare form of cancer,” his agent confirmed to CNN Sports on Thursday.

“Bryan Braman was a warrior in every sense — on the field and in life — facing every battle with unshakeable grit and heart,” Sean Stellato said. “His passing leaves a void not just in football, but in the spirit of every underdog who ever dared to fight.”

According to a GoFundMe page which was organised to help fund his treatment and medical necessities, Braman had been diagnosed with cancer in February.

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In the latest update on the page from June, it said that Braman had undergone multiple “surgical procedures” at a facility in Seattle but had been unable to fully recover due to his lowered immunity.

The latest post added that Braman had returned home after undergoing Car T cell reprogramming treatment. According to the National Cancer Institute, Car T cell therapy involves genetically engineering a patient’s own T cells — part of the body’s immune system — to attack cancer cells.

Although there were signs of optimism as the “mass did start to shrink,” the cancer “started fighting back.” As a result, Braman underwent chemo treatments, but the cancer grew “exponentially faster” around his vital organs.

At the time of writing, the GoFundMe had raised almost $90,000. Braman’s former Houston Texans teammate, JJ Watt, donated $10,000 to the cause.

Watt later paid tribute to Braman on social media, writing: “Rest in Peace brother. Gone far too soon.”

Stellato posted a framed, signed jersey from Braman on his Instagram story with the caption: “My heart hurts. I love you Bryan.”

Braman began his college career at Idaho before moving to Long Beach City College and finishing at West Texas A&M.

Having gone undrafted, he signed with the Texans in 2011 as an undrafted free agent.

Braman became a fixture of Houston’s special teams unit. He became a fan favourite after making a tackle with no helmet on during a game against the Tennessee Titans in 2011.

In 2012, he was named a Pro Bowl special teams alternate.

Braman spent three years in Houston before signing with the Philadelphia Eagles. He spent four seasons — including a brief spell on the New Orleans Saints practice team — with the Eagles.

In his final NFL season, he was part of the Eagles team which won Super Bowl LII, beating the New England Patriots.