Chris Johnson still holds the NFL record for the most scrimmage yards in a single season. Now, the former running back is facing a serious illness.

Former professional football player Chris Johnson has been diagnosed with ALS, an incurable neurological disease. He received the diagnosis last year, and now he wants people to know “that I’m still me,” the 40-year-old former running back said in an interview with “Good Morning America”: “ALS has changed what my body is capable of, but it hasn’t changed who I am.”

Johnson, who spent his most successful years with the Tennessee Titans from 2008 to 2013, is the leader of an exclusive group in the NFL. In 2009, the then-24-year-old racked up a total of 2,509 yards from scrimmage—that is, by running with the ball or catching it—in an outstanding season; that remains the NFL record to this day.

That same year, Johnson was named Offensive Player of the Year. After his successful stint in Tennessee, Johnson also played for the New York Jets and the Arizona Cardinals.

Johnson Wants to Fight

After the shock of the diagnosis, he realized “that you have two options,” Johnson said: “You can give up, or you can fight. I chose to fight.”

The Titans also expressed their sympathy in a statement: “Some people leave a mark on an organization that simply cannot be put into words,” said majority owner Amy Adams Strunk: “Chris Johnson is one of those people for us.”