Rams receiver Cooper Kupp out for season with torn knee ligament

The roles mainly have been cameos, short stints as a fill-in starter for other Rams receivers.

Now Josh Reynolds is preparing for a longer stay in the lineup.

Coach Sean McVay announced Monday that Cooper Kupp would not play again this season after tests revealed that the second-year pro had suffered a torn anterior cruciate ligament in his left knee during Sunday’s victory over the Seattle Seahawks at the Coliseum.

Kupp is expected to have surgery as soon as this week, McVay said.

“It’s a huge loss for our football team,” McVay said. “He’s such an important part of what we do.”

Kupp, a 2017 third-round draft pick from Eastern Washington, teamed with Robert Woods and Brandin Cooks to give quarterback Jared Goff one of the NFL’s most dynamic pass-catching trios.

Kupp has caught 40 passes for 566 yards and six touchdowns. He caught five for 39 yards Sunday before he was injured during the fourth quarter on a play that went to the opposite side of the field.

It was the third injury of the season for Kupp. He suffered a concussion in Week 5 against the Seahawks and a left knee sprain in Week 6 at Denver. Kupp sat out against the San Francisco 49ers and Green Bay Packers before returning in Week 9 and scoring a touchdown against the New Orleans Saints.

During Kupp’s absences, Reynolds stepped in and performed well.

Reynolds, a 2017 fourth-round draft pick from Texas A&M, has seven catches for 98 yards. He caught two touchdown passes in Week 8 against the Packers.

“Josh Reynolds has definitely demonstrated he’s more than capable,” McVay said. “He is a starting-caliber player.”

Reynolds is looking forward to playing in the six remaining regular-season games and the playoffs.

“Now I can get the feel for the game, and the game can get slower for me,” he said. “As that goes, I get better as it goes too.”

Discipline coming?

Defensive tackle Aaron Donald could be fined by the NFL for his actions immediately after Sunday’s game, which included several personal-foul and unsportsmanlike-conduct penalties against the Rams.

Donald had taken off his shoulder pads, but he put on his helmet and went to the middle of the field and confronted Seahawks center Justin Britt, grabbing Britt’s facemask.

During the fourth quarter, Donald had scooped up what he thought was a fumble by Seahawks quarterback Russell Wilson — it was an incomplete pass — and run with the ball until he was forced out of bounds on the Rams sideline. Britt delivered a hit that sent Donald sprawling.

Donald got up and grabbed Britt’s facemask, and both players drew unnecessary roughness penalties.

Donald declined to speak with reporters Monday before the Rams left for Colorado Springs, Colo., where they will train in preparation for next Monday night’s game against the Kansas City Chiefs in Mexico City.

McVay said he saw the incident and had spoken to Donald.

“We can’t allow the emotions of the game to affect our responses that could potentially hurt the team — and something bad could’ve happened to him,” McVay said. “We’ve got to avoid those situations.”

Etc.

Kick returner/receiver Pharoh Cooper (ankle) is ready to return to practice but the Rams have not determined whether they will recall him from injured reserve. “That’s something that you can expect to have a little bit more clarity on that as the week progresses,” McVay said. NFL teams can recall only two players from injured reserve, and cornerback Aqib Talib is expected to be activated in Week 13 against the Detroit Lions. … McVay said the Rams would provide a second charter plane to Colorado during the week if players’ families affected by the fires in Ventura and Los Angeles counties want to join them in Colorado. … The Rams finalized plans to play a 2019 preseason game at Aloha Stadium in Honolulu. The opponent, date and time are still to be determined.

gary.klein@latimes.com

Twitter: @latimesklein