SAN FRANCISCO — Dwight Clark revealed Sunday that he has Lou Gehrig’s disease and suspects playing football might have caused the illness.

Clark announced on Twitter that he has amyotrophic lateral sclerosis, a disease that attacks cells that control muscles. The former San Francisco 49ers wide receiver linked to a post on his personal blog detailing his ALS diagnosis, but the site crashed Sunday night, apparently from an overflow of traffic.

“I’ve been asked if playing football caused this,” Clark said in the post. “I don’t know for sure. But I certainly suspect it did.”

The 60-year-old Clark wrote that he began experiencing symptoms in September 2015.

RELATIVES OF Pro Football Hall of Famer Gale Sayers say the Chicago Bears legend has been diagnosed with dementia.

His wife, Ardythe Sayers, told The Kansas City Star that her 73-year-old husband was diagnosed four years ago and she blames Sayers’ football career. He played for the Bears from seven seasons starting in 1965 after setting records at the University of Kansas.

JETS: New York signed veteran free-agent quarterback Josh McCown to a one-year deal.

Agent Mike McCartney announced Monday on Twitter that the contract is for one season.

McCown met with the Jets over the weekend, but left Sunday without a deal. The sides agreed to a contract a day later.

McCown, who’ll turn 38 on July 4, played the past two seasons with Cleveland.

GIANTS: The team is giving former New York Jets quarterback Geno Smith a chance to learn from veteran Eli Manning.

The Giants on Monday announced they had signed Smith and cornerback Valentino Blake, who also excels on special teams.

A second-round draft choice out of West Virginia in 2013, Smith has been a bust after a good rookie season.

He missed most of last season after surgery for an ACL injury in October.

BEARS: Chicago re-signed safety Chris Prosinski to a one-year contract.

Prosinski played in 16 games and had 15 tackles and one pass breakup last season – his second in Chicago. He also finished third on the team with seven special teams tackles.

Prosinski has 120 tackles and 43 special teams tackles for Jacksonville (2011-14), Philadelphia (2014) and Chicago (2015-16).

COWBOYS: Dallas re-signed backup quarterback Kellen Moore. Before Moore broke his right ankle during the first week of training camp last year and missed the entire season, he had been expected to back up Tony Romo.

When Moore was hurt, rookie quarterback Dak Prescott got his chance after Romo got hurt in his first preseason game. Prescott, the fourth-round draft pick, became the starter and helped lead the Cowboys to the NFC East title.

RAIDERS: Oakland signed former first-round pick EJ Manuel as a backup quarterback and linebacker Jelani Jenkins.

STEELERS: Pittsburgh signed free agent running back Knile Davis and free agent cornerback Coty Sensabaugh, regrouping after missing out on coveted linebacker Dont’a Hightower by finding depth at two areas of need heading into 2017.

BENGALS: Cincinnati signed linebacker Kevin Minter to a one-year deal, filling the opening from Karlos Dansby’s departure for Arizona as a free agent.

Minter is entering his fifth season.

THE NFL IS ramping up its educating and training for women interested in working in football operations.

The league’s second women’s career development symposium will be held Friday and Saturday in Phoenix, just before the owners’ annual meetings. More than 40 women from across the NFL will learn about football administration, operations, coaching and scouting through presentations, panel discussions, breakout sessions and networking opportunities with club and league executives.