49ers linebacker Fred Warner placed on Reserve/COVID-19 list

Linebacker Fred Warner, one of the 49ers’ best defensive players, has been placed on the Reserve/COVID-19 list, the team announced Monday.

The Reserve/COVID-19 list is for a player who either tests positive for the coronavirus or has been quarantined after having been in close contact with an infected person. NFL teams are not allowed to disclose whether a player has tested positive.

If Warner, 23, has tested positive for the virus and is asymptomatic, he needs to pass two coronavirus tests and could return as soon as five days after his initial positive test. If Warner has tested positive and has symptoms, he can’t return until 10 days have passed since his symptoms first appeared.

The 49ers will open the regular season against the Cardinals on Sept. 13 at Levi’s Stadium.

Warner, who missed Sunday’s practice, is the third 49ers player to be placed on the COVID-19 list this season, and the first since running back Jeff Wilson on July 30. Wilson was activated from the list after he was sidelined for five days. Wide receiver Richie James was activated from the list on Aug. 4 after an eight-day absence.

Warner is one of four NFL players on the COVID list, joining Saints running back Dwayne Washington, Panthers defensive back Derrek Thomas and Falcons defensive end Steven Means.

Warner, a 2018 third-round pick, was a Pro Bowl alternate last season and led the NFL’s second-ranked defense with 118 tackles while adding nine pass-breakups, three sacks, three forced fumbles and an interception he returned 46 yards for a touchdown.

He enjoyed a stellar training camp this summer, sessions marked by aggressiveness and sideline-to-sideline speed.

“While he’s not in here, I’m sure he’s in his apartment doing bag drills or wherever he’s living, just going crazy that he can’t be in here,” head coach Kyle Shanahan said. “So Fred’s a stud. Whenever he can come back, he will be ready to go.”

Injury report: Linebacker Dre Greenlaw missed his second straight practice Monday because he is in the concussion protocol, Shanahan said. … Cornerback K’Waun Williams (calf) returned to practice after he was injured early in training camp. … Tight end George Kittle missed his fourth straight practice with what Shanahan has termed a “tight hamstring.” He said Kittle should return to practice “later this week.” … Left tackle Trent Williams was given a vet day.

Cutout program: The 49ers announced fans can purchase cutouts of themselves that will be placed on a seat behind one of the end zones at Levi’s Stadium this season.

The cutouts cost $149 with proceeds benefiting the 49ers foundation and other team-related charitable programs. Cutouts can be purchased at 49ers-fan-cutouts.aaaflag.com.

The 49ers have announced no fans will attend their regular-season opener against the Cardinals on Sept. 13. No decision has been made about fans attending their final seven regular-season home games.