End zone: Former Pittsburgh Steelers outside linebacker James Harrison went unclaimed in the NFL’s waiver process, making him a free agent to sign with any team. The Ravens have been rumored as one of those teams that might add Harrison, who had a brief stint in Baltimore in 2003. But Harbaugh was tight-lipped about that possibility, referring such questions to the front office. “I don’t know,” he said. “You’ll have to ask [general manager] Ozzie [Newsome].” … Harbaugh called Maxx Williams “remarkable” considering that the tight end has played in 10 games this season after sitting out the final 12 games last year to undergo a rare surgery to repair what Harbaugh had once described as cartilage damage. “He came back from a knee injury that as you guys know had never been done before — at least in football,” Harbaugh said of Williams, who made second career touchdown catch against the Colts and first since a 21-yard score on Nov. 15, 2015. “I don’t know if an athlete’s ever done it before. That would be a good question for Maxx or the guys, the doctors. But he’s a good player. I think Maxx doesn’t always get the credit that he deserves. He’s a very physical player. He plays really hard. He’s a factor out there. People know where he’s at, they have to. He’s got good hands. He makes the contested catches. He’s not the prettiest athlete in the world. That’s probably what people see sometimes, and that’s OK. People like pretty. Maxx isn’t that as an athlete, but he’s tough and he’s a good football player and I’m sure glad we have him.” … The Ravens announced they added cornerback Robert Nelson Jr. to the practice squad. Nelson, who had been released by the New York Jets on Dec. 8, fills the vacancy created by Adeboyejo’s promotion.