SANTA CLARA, Calif. — What stands out about rookie receiver De’Zhaun Stribling, Brock Purdy said Monday, is he doesn’t look like a rookie receiver.“The way he runs routes, the detail of it — obviously, we’re coaching him up on some stuff and whatnot,” the San Francisco 49ers quarterback said after practice. “But more than anything, he’s come in and understands the route depth, the details, the alignments in our offense. And all those things are really tough for rookies. It’s not easy. It’s a whole other language.”The detail Kyle Shanahan demands from his receivers is the reason most fail to make an impact during their rookie seasons. And the ones who have — such as Deebo Samuel in 2019 and Brandon Aiyuk the next year — have noted how hard Shanahan was to satisfy.Stribling, the team’s top pick in April, is off to a strong start. During a Monday practice that was notable for its tough, sticky coverage by defensive backs, Stribling caught passes from Purdy, Mac Jones and Kurtis Rourke, including a deep crosser from Jones that was one of the offense’s biggest gains of the session.3 players to watch at 49ers training campMatt BarrowsThough smaller receivers such as Jacob Cowing seemed to struggle with the aggressive coverage, the 6-2, 207-pound Stribling looked comfortable over the middle where he used his frame to shield the ball from defenders.“He’s done a good job with the footwork and getting off the line and stuff,” Purdy said. “But the other half of football is up top — using your hands as a receiver and trying to create separation, obviously legally. But that’s a part of (being a receiver) — using your strength against a DB and stuff.”Added Purdy: “He’s proving to all of us that he’s reliable and we can trust him. But it is Day 2 of camp, and we’ve got to continue to find out (more). But I’ve got a lot of trust in him now.”Odds and ends• Stribling and the team’s young receivers are getting a few more snaps than planned because of an injury to veteran Christian Kirk, who walked off the field Sunday with what turned out to be a calf strain. The 49ers didn’t give a timetable for his return, but calf strains typically are multiweek injuries.