Kyle Shanahan is not ready to put rookie wide receiver Jason Cowing in the mix yet, even though Brandon Aiyuk and Ronnie Bell had their challenges in the 49ers’ Week 3 loss to the Los Angeles Rams on Sunday at SoFi Stadium.

Shanahan did not get into specifics why Cowing isn’t ready to join the offense on the field, but made it clear it is not going to happen after the 49ers’ struggles in Los Angeles.

“There’s lots of reasons that go into it,” Shanahan said said via conference call on Monday. “But he hasn’t been able to make his way into that group yet, and the more he gets comfortable with the offense and the more consistent he gets then he’ll earn those opportunities.”

Cowing appeared to have an upward trajectory during rookie minicamp and the beginning of training camp until he was sidelined with a hamstring injury. While the Arizona product has been utilized as the punt returner, his time to contribute on the offense still is to be determined.

With Deebo Samuel (calf), Christian McCaffrey (Achilles/calf) and George Kittle (hamstring) sidelined with injuries, the 49ers are looking for bigger contributions from their other receiving playmakers.

Jauan Jennings proved he can be the star of the show, catching 11 of his 12 targets for a career-high 175 yards and three touchdowns against the Rams. But Aiyuk caught five of his 10 targets while Bell had an even tougher day, catching only one of his three targets in the loss.

“[Cowing’s] still working to get out there,” Shanahan said. “He is trying to get more comfortable with the offense and just earn a role with it, gets closer and closer each week. Still got a bit to go though.”

Shanahan’s playbook is a challenge for most young wide receivers and history has shown that rookies coming joining the 49ers have experienced an extensive learning curve. Missing training camp is proving to have slowed the process for Cowing.

Cowing told NBC Sports Bay Area after Sunday’s loss that he is using the veteran receivers in the room as resources to improve and get ready for his opportunity.

“Definitely,” Cowing said. “[Jennings has] been helping me since Day 1. I’ve been watching everything he does, listening to everything he says. All of them — Deebo, Brandon — all of them. All good people.”