SANTA CLARA, Calif. — When backup left tackle Vederian Lowe limped off the field with a high ankle sprain midway through the San Francisco 49ers’ first training camp practice last week, any number of players could have jumped in to replace him.There was Austen Pleasants, who was in the No. 2 role last year and started a Week 18 game against the Seattle Seahawks. Brandon Parker has been in the league since 2018, the past two years as a member of San Francisco’s practice squad. Even International Pathway Program player Isaac Alarcon was a good candidate considering he’s in his third 49ers training camp.Instead, the least experienced of them all, rookie Enrique Cruz Jr., bounded into the huddle like an eager golden retriever, and the second-team offense didn’t skip a beat.“Coach, who goes in?” Cruz recalled excitedly asking Chris Foerster. The offensive line coach’s quick response: “You! You go in!”The sequence ended up being a good way to get rid of Day 1 jitters, Cruz said. And it offered a glimpse at one of the rookie’s top qualities: He isn’t shy.“He has an infectious personality,” Cruz’s high school coach, Nick Hildreth, said. “He’s fun, he’s so outgoing, he’s so happy to be there. I’ve never seen him where he’s negative toward anybody, ever.”Early standouts from 49ers training campVic Tafur and Matt BarrowsCruz is very much a project. He was the last of the 49ers’ draft picks in April, going late in the fifth round at No. 179. And barring a flurry of injuries at his position, he’s unlikely to see the field this season.Still, he’s the first true offensive tackle — a college tackle the 49ers intend to keep at that position — they’ve drafted in five years, and his athletic skills compare to those of the team’s most recent left tackles, Joe Staley and Trent Williams. The idea of anyone replacing Williams, a 12-time Pro Bowler who is still going strong at age 38 and plans to play two more seasons, is daunting, but Cruz has skills worth developing.