The hottest-selling NFL jersey doesn’t belong to Tom Brady or Von Miller or Aaron Rodgers. Or any of the NFL many stars, for that matter. It belongs to a rookie who has no chance of starting for his team this season.

It belongs to Steelers RB James Conner, the team’s third-round pick in the 2017 NFL draft.

If you’re familiar with Conner’s story, you know why he’s leading the entire league in jersey sales. If you don’t, you’ll understand soon enough.

Conner was a star running back at Pitt. He rushed for 1,765 yards and 26 touchdowns en route to winning ACC player of the year in his sophomore season. A college star being drafted by his local NFL team certainly boosts jersey sales, but that’s not why his jersey is flying off the shelves now. What happened the following season endeared him to football fans in Pittsburgh and around the country.

Via USA TODAY Sports’ Nicole Auerbach:

“But while I’m lifting I can see that I’m getting out of breath really fast,” Conner says. “I’m straining my face. I swell up and get puffy, swollen. I have dizziness a lot”… “Conner had tried different antibiotics. Doctors thought perhaps it was a sinus infection. That is, until the antibiotics had no effect. For weeks, no one could figure it out. “Finally, Conner visited an ear, nose and throat specialist, who ruled out any issues with Conner’s sinuses and then ordered an X-ray on his chest, which eventually led to a positron emissions tomography (PET) scan — and the discovery of a large tumor.”

Conner was diagnosed with Hodgkin’s Lymphoma and immediately started chemotherapy. He continued working with the team in non-contact drills throughout the treatment. After 12 rounds of chemo, Conner announced he was cancer free.

Conner returned to the field for Pitt’s 2016 season opener and did not miss a game.

He ran for 1,092 yards and 16 touchdowns before declaring for the NFL draft in December.