Dwight Clark, the former San Francisco 49ers wide receiver known for hauling in “The Catch” from Joe Montana to secure a win over the Dallas Cowboys in the 1981 NFC Championship Game, revealed Sunday he has been diagnosed with amyotrophic lateral sclerosis (ALS), or Lou Gehrig’s disease.

Clark, 60, said he underwent months of testing after first experiencing weakness in his left hand in September 2015.

“In addition to losing strength in my left hand — which makes opening a pack of sugar or buttoning my shirt impossible — I have now experienced weakness in my right hand, abs, lower back and right leg,” Clark wrote. “I can’t run, play golf or walk any distances. Picking up anything over 30 pounds is a chore. The one piece of good news is that the disease seems to be progressing more slowly than in some patients.”

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A two-time all-pro and Super Bowl champion, Clark trails only Jerry Rice and Terrell Owens in career receiving yards (6,750) for the franchise and had his No. 87 jersey retired in 1988. He also served as general manager for the 49ers in 1998 and the Cleveland Browns from 1999-2001.

“I’ve been asked if playing football caused this,” Clark wrote. “I don’t know for sure. But I certainly suspect it did. And I encourage the NFLPA and the NFL to continue working together in their efforts to make the game of football safer, especially as it relates to head trauma.”