Rams catch a break when Raiders trade Khalil Mack to the Bears

A day after the Rams got stronger by signing defensive lineman Aaron Donald to a record-setting extension, their season-opening opponent got weaker by trading a star defensive player.

The Oakland Raiders’ decision Saturday to trade holdout edge rusher Khalil Mack to the Chicago Bears seemingly gives the Rams an edge heading into their Sept. 10 opener against the Raiders on “Monday Night Football.”

Donald, the reigning NFL defensive player of the year, and Mack, the 2016 winner, both sat out training camp and the preseason to pressure their teams into giving them new deals.

It appeared one might be waiting for the other to sign first, so that a new compensation benchmark could be set and topped.

On Friday, Donald received a record $135-million extension, with $87 million guaranteed. He said Mack’s holdout was not a factor in how his negotiations played out.

“Not at all,” Donald said. “We were just trying to find a way to get it done, wasn’t worried about other things.”

The Rams will still have to deal with Mack later in the season because he reportedly agreed to a $141-million extension with the Bears.

The Rams play the Bears at Chicago on Dec. 9.

Hemingway cut

A tight end trio of Tyler Higbee, Gerald Everett and Temarrick Hemingway was expected to help the Rams’ prolific offense become even more proficient this season.

The tight ends might become a viable threat, but Hemingway will not be part of it.

Hemingway was among players cut Saturday by the Rams as NFL rosters were trimmed from 90 to 53 players.

Hemingway, a sixth-round draft pick in 2016, was sidelined last season after suffering a broken leg. But he appeared to come back strong during offseason workouts and minicamp.

Going into training camp, coach Sean McVay sounded enthused about the combination of Higbee, Everett and Hemingway.

Hemingway, however, struggled during the preseason, dropping several passes.

The Rams also released tight end Henry Krieger-Coble, meaning Johnny Mundt is the third tight end.

The Rams signed Mundt, who played at Oregon, in 2017 as an undrafted free agent. He was on the practice squad for much of last season and played in two games.

Mundt caught seven passes for 57 yards this preseason, including four for 40 yards in Thursday’s loss at New Orleans.

Nine of the Rams’ 11 draft picks in the 2018 draft made the roster, including running back John Kelly, offensive linemen Joseph Noteboom, Brian Allen and Jamil Demby, defensive linemen John Franklin-Myers and Sebastian Joseph-Day and linebackers Micah Kiser, Justin Lawler and Trevon Young.

Linebacker Travin Howard, a seventh-round draft pick from TCU, was waived with an injury.

Linebacker Ogbonnia Okoronkwo was placed on the physically unable to perform list. Okoronkwo is recovering from foot surgery.

Linebacker Ejuan Price and cornerback Dominique Hatfield, members of the team in 2017, were among players released Saturday.

Others included quarterback Luis Perez, receivers KhaDarel Hodge and Steven Mitchell, defensive backs Steven Parker and Ramon Richards and running back Larry Rose.

The Rams can continue to make moves as they peruse players released by other teams.

This was their roster at Saturday’s deadline:

Quarterbacks: Jared Goff, Sean Mannion, Brandon Allen.

Running backs: Todd Gurley, Malcolm Brown, Justin Davis, John Kelly.

Receivers: Robert Woods, Brandin Cooks, Cooper Kupp, Pharoh Cooper, Mike Thomas, Josh Reynolds.

Tight ends: Tyler Higbee, Gerald Everett, Johnny Mundt.

Offensive line: Andrew Whitworth, Rodger Saffold, John Sullivan, Austin Blythe, Rob Havenstein, Joseph Noteboom, Brian Allen, Jamil Demby.

Defensive line: Aaron Donald, Ndamukong Suh, Michael Brockers, Ethan Westbrooks, Tanzel Smart, John Franklin-Myers, Sebastian Joseph-Day.

Linebackers: Mark Barron, Cory Littleton, Samson Ebukam, Matt Longacre, Dominique Easley, Ramik Wilson, Bryce Hager, Micah Kiser, Justin Lawler, Trevon Young.

Cornerbacks: Marcus Peters, Aqib Talib, Nickell-Robey Coleman, Sam Shields, Troy Hill.

Safeties: Lamarcus Joyner, John Johnson, Marqui Christian, Blake Countess, Isaiah Johnson

Specialists: Kicker Greg Zuerlein, punter Johnny Hekker, snapper Jake McQuaide.

L Aaron Donald is on NFL exempt list.

Special delivery

The starting offense did not play during the preseason, and the defense played only seven snaps.

Zuerlein and Hekker, though, got plenty of work.

Zuerlein, coming off December back surgery, made three of four field-goal attempts and also kicked off several times.

“Physically, I feel ready to go,” he said. “Technique-wise I’m still not quite where I want to be yet.

“Fortunately, we have a couple extra days, five practices or so to get really dialed in.”

Hekker averaged 41.8 yards for 12 punts in three preseason games. Hekker punted in the first half and then gave way to Sam Ficken, a kicker who was released Friday.

“It’s a delicate balance of getting good work in the first half and not really fretting over not getting enough work,” he said. “There’s always room to grow as a specialist — you’re never where you want to be and I think that’s good quality to have. I think Greg,Jake and myself all kind of share that as well.

“We never arrived. We all have things in our techniques we can clean up on and efficiency we can build. And just working to make sure when [Sept. 10] comes around we’re at our best.

Etc.

The Rams were off Saturday, but will resume practice Sunday. They are off Monday and then begin game-week preparations for the Raiders.

gary.klein@latimes.com

Follow Gary Klein on Twitter @latimesklein