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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.

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Though 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.

Meanwhile, backup left tackle Vederian Lowe on Sunday suffered a high-ankle sprain, which also is typically a multiweek recovery. Austen Pleasants and rookie Enrique Cruz Jr. filled in with the second- and third-team units.

Rookie defensive tackle Gracen Halton (knee bone bruise) and edge rusher Andrew Farmer (back) were out Monday. Cornerback Nate Hobbs was back after missing Sunday’s practice with an illness.

• There were a few tense moments Monday when third-round pick Romello Height was carted off the field after dropping to the ground. It turns out the defensive end was dealing with what defensive coordinator Raheem Morris described as “severe cramps.”

“He gave me a thumbs up, so I knew right away (Height was OK),” Morris said.

With Mykel Williams (knee) on the physically unable to perform list and Nick Bosa (knee) held out of team drills, Height has been working with the first-string defense opposite Keion White. He projects as the 49ers’ pass rush specialist this season, similar to the role Bryce Huff had last year.

• On defense, the most impressive player so far has been middle linebacker Fred Warner, who stuffed Christian McCaffrey on a running play early in practice and then later blew up a would-be screen pass. The linebacker punctuated that feat with a “tweet that” signal to nearby reporters.

Newcomer cornerback Jack Jones also has stood out over the first two days of practice, including when he broke up a pass over the middle from Mac Jones to Stribling midway through practice. Aggressive cornerback play was a theme Monday, as Renardo Green and nickel cornerback Upton Stout got their hands on the ball to break up short passes.

Safety Ji’Ayir Brown did a good job of digging a short pass from Purdy off the ground for an interception. Rourke was beaten by veteran cornerback Eli Apple, who jumped a slant-pattern pass to Junior Bergen.

• Purdy was a respectable 8 of 13 during team drills, although the bulk of his completions were short attempts and checkdowns to tailbacks. One asterisk: Green was flagged for pass interference on a deep-ball attempt from Purdy to Mike Evans.

The deepest pass of the day came from Rourke, who connected with Bergen on a long ball at the sideline. Rourke, who is competing to be the No. 3 quarterback, was 4 of 5 during team sessions.

• As was the case Sunday, Shanahan emerged from his office toward the beginning of the team period, then watched 45 minutes of practice next to general manager John Lynch well behind the defense. Though he’s still dealing with concussion symptoms resulting from a July 14 vehicle collision, Shanahan showed good instincts in scrambling out of the way on Purdy’s deep-ball attempt to Evans.

• Third-round draft pick Kaelon Black looked explosive for the second straight day. His competition for backup tailback, Jordan James, didn’t take part in the last third of practice. He was being checked out by trainers after practice, and there were no immediate details on an injury.

• As has been the case since the spring, Malik Mustapha and Marques Sigle alternated series with the first-team defense.

• Nick Martin, who took snaps at weakside linebacker last year, has been lining up at both strongside (with the first-team defense) and weakside (with the second team) this summer. If he wins the strongside job, he’d be in position to start the Week 1 game in Australia against the Los Angeles Rams.

• The 49ers are conducting their first-ever “jog-through” practice of training camp Tuesday and will not have any media availability. They’ll have their most intense practice so far Wednesday, followed by a league-mandated players day off Thursday.