KANSAS CITY, Mo. — The Kansas City Chiefs remained without All-Pro safety Tyrann Mathieu after his positive test for COVID-19 as the two-time defending AFC champions began preparing Monday for their season opener against the Cleveland Browns.

Chiefs Coach Andy Reid said that Mathieu, who was vaccinated against the virus, remained in the league’s protocol, which means he had yet to return two negative tests taken 24 hours apart. That is the requirement for vaccinated players who are asymptomatic to return to their teams under the NFL rules released in July.

“We just have to wait that out and see where he’s at,” Reid said. “I’ll know more as we go on.”

The Chiefs are off Tuesday before returning for their first on-field work of game week Wednesday. They will also have a full practice Thursday before their typical quick Friday practice and Saturday walk-through, which means there is still a chance Mathieu will be able to join the Chiefs before the Browns visit Arrowhead Stadium on Sunday.

Mathieu starts in the base defense alongside Daniel Sorensen. And while the Chiefs have a pair of capable backups in Juan Thornhill and Armani Watts, Mathieu is the leader of a secondary that has become one of their defensive strengths.

He is coming off his second straight All-Pro season, and possibly the best of his career, picking off a career-high six passes with 62 tackles and three for loss. One of those interceptions came in a divisional playoff win over the Browns in January.

DOLPHINS: Miami placed presumed starting left tackle Austin Jackson and backup tight end Adam Shaheen on the COVID-19 reserve list, calling into doubt their availability for the team’s opener at New England.

Dolphins Coach Brian Flores said “it’s possible” that both could be in the lineup on Sunday. That would suggest Shaheen did not test positive; under NFL rules, unvaccinated players are out at least 10 days if they test positive and out at least five days if they are deemed to be a close contact with someone who has been exposed.

Shaheen, a backup behind starter Mike Gesicki, is unvaccinated. He was on the COVID list last month as well because of contact tracing and said he would not be vaccinated — even though that means he is tested daily, as opposed to weekly testing for players who are vaccinated.

JETS: Wide receiver Jamison Crowder is still recovering from symptoms of COVID-19 and his status for the opening game at Carolina remains uncertain.

Coach Robert Saleh said that Crowder is vaccinated against the virus, but the receiver’s availability for the season opener will depend on how he feels and tests. As a vaccinated player, Crowder will also need to produce two negative tests 24 hours apart, per NFL protocols.

“We’re just taking it a day at a time,” Saleh said during a video call.

Crowder was placed on the reserve/COVID-19 list last Friday after testing positive for the coronavirus. Saleh said Crowder’s case was an isolated incident and he had no close contacts on the team.

49ERS: Rookie quarterback Trey Lance showed signs of progress in returning from a finger injury but there are still questions about whether he will be able to play in the season opener.

Lance no longer needed a splint on the index finger on his throwing hand after suffering a small chip fracture in the exhibition finale on Aug. 29. But during the open portion of practice for reporters, Lance didn’t make any throws.

He held a ball during an early drill but practice squad quarterback Nate Sudfeld took warmup throws behind starter Jimmy Garoppolo. Lance didn’t take snaps from center and only went through the motions on his footwork in the backfield before making fake throws.

PANTHERS: Starting right guard John Miller has been placed on the COVID-19 reserve list and will miss Carolina’s home opener on Sunday against the New York Jets.

Panthers Coach Matt Rhule said Miller will be out 10 days, which according to league rules would indicate that he was an unvaccinated player who tested positive. Rhule said last week that only two of the team’s players had not been vaccinated.

Rhule said Dennis Daley will start in his place.

WASHINGTON: Wide receiver Curtis Samuel took part in Washington’s Labor Day practice and looks like a candidate to play in the season opener against the Los Angeles Chargers after missing training camp.

Washington signed Samuel to a $34.5 million, three-year contract in the hopes of adding his skillset to an offense that struggled last season. Samuel spent time on the NFL’s COVID-19 list and has been hampered by a groin injury since offseason workouts.