SAN JOSE, Calif. — If you’d asked Fred Warner six months ago whether he knew how to swim, the answer would have been: sort of.The San Francisco 49ers’ middle linebacker moved through the water like a lot of people who have never had formal lessons — head up, legs down, a lot of splashing, very little efficiency.Said Sage Hopkins: “He was at Level 1 — not drowning, but if he fell off of a boat far from shore, he likely wouldn’t have made it back.”Hopkins, 53, is in position to judge. He was a junior lifeguard as far back as elementary school, and he’s lived on the North Shore of Oahu in Hawaii, where he regularly surfed 20-foot waves and occasionally rescued distressed swimmers. For the past 21 years, he’s been the women’s swim and dive coach at San Jose State.That’s where he met Warner, who arrived at the school’s immaculate outdoor pool one day in late November looking for a way to accelerate his rehabilitation from a broken and dislocated ankle.Hopkins noticed two things right away.One was Warner’s star power. The walk from the pool to the university parking garage takes you past the windows of the student recreation center. When the 6-foot-4, 236-pound Warner made that trek the first time, he was noticed immediately, and the building emptied en masse.“He stopped, took a picture with every single person that asked and then had a meaningful interaction with each of them,” Hopkins recalled. “It took a good 20 minutes to walk a hundred yards. I think they were so starstruck. I still see people freeze almost into a momentary catatonic state when he walks up. It happens pretty regularly.”Hopkins also quickly realized Warner wanted — badly — to be pushed hard.His injury had occurred seven minutes into an Oct. 12 road loss to the Tampa Bay Buccaneers when teammate Ji’Ayir Brown inadvertently crashed into his lower leg. Warner, who had missed just one game in 7 1/2 seasons, looked down to find his right foot facing the wrong direction. He watched teammates and opponents alike glance at his foot, then frantically summon medical help.“I remember laying down on my side and kind of just waiting for them to get to me,” he said. “And Dr. (Tim) McAdams came up, and it’s — pop, pop! — he snapped it right back. He didn’t really say much to me. He just kind of held my leg, and he snapped it right back. I felt like a crunch.“And then I remember being on my back, and I see Kyle (Shanahan) come to me, Robert (Saleh), and then all my teammates. And they’re all kind of saying, ‘Sorry, buddy.’ And I’m like, ‘I know. I’m good. Don’t worry. I’ll be fine.’”Fred Warner, right, with head team physician Tim McAdams after he was injured in Tampa, Fla., in October. (Mike Ehrmann / Getty Images)Warner isn’t the type to drape a towel over his head and go into woe-is-me mode. In fact, as he was being carted away, television cameras caught him serenely chatting with McAdams, who was concentrating on stabilizing his lower leg. Warner noted things became more hectic as the cart disappeared into the stadium tunnel.“I was telling McAdams I didn’t even get a chance to protect myself, I never even saw it coming,” he said. “And then immediately my mind went to, ‘Oh, no, my mom and my wife just saw that. And everybody in my family.’ So it was, ‘Oh, somebody give me my phone! I’ve got to call my wife! I’ve got to call my mom!’”Warner had surgery two days later. Early on, he said there was “zero talk” about playing again that season. Instead, the plan was for a methodical rehabilitation. Like many veterans, Warner usually doesn’t take part in spring OTA practices. The next time he’d suit up was training camp, which afforded him an unhurried, nine-month comeback. And he was fine with that.