Football fans and pundits frequently reach back to say or post, “Welcome to the NFL,” this time of year.

It’s a four-word phrase – if not a four-letter word – that illustrates how quickly things can change, namely when a team’s Week 1 highs get pancaked by Week 2 lows.

But it also works both ways.

The Los Angeles Rams proved that on “Monday Night Football,” thumping the visiting New York Giants 28-6 in a remarkable rebound from a season-opening dud against the San Francisco 49ers in Melbourne, Australia, on Sept. 10.

“Sometimes you win, sometimes you learn,” Rams coach Sean McVay said. “And sometimes you have a dumbass coach that makes travel plans that put you in a bad spot.”

On Monday, the Rams relied on another conditional they hope remains constant. Sometimes, Aaron Donald plays nearly 60 percent of your defensive snaps after coming out of retirement.

Throughout the Los Angeles locker room, players cited the return of No. 99 to the defensive line as a leading reason they prevailed.

Quarterback Matthew Stafford admitted Donald’s jubilation while running out of the tunnel made Stafford “so juiced” that “I couldn’t control myself.”

He was speaking figuratively, of course, because Stafford completed 71 percent of his passes for 327 yards and four touchdowns, including two scores to Davante Adams.

The performance of Stafford’s counterpart, Jameis Winston, impacted the game significantly, too. Thrust into action after Giants franchise QB Jaxson Dart exited with a left-knee injury after just seven snaps – “in the neighborhood” of an MCL sprain, coach John Harbaugh said – Winston sputtered.

And that may be putting it mildly.

Winston completed just 11-of-27 passes for 111 yards and interception while leading the Giants only to a pair of Dominic Zvada field goals.

“We have to execute better,” Winston said. “We are focusing on being in better down-and-distance. We were in third-and-long a lot, so we have to execute better; I have to execute better on first and second down.”

Easier said than done with Donald looming on the other side of the line of scrimmage.

Still ramping up after ending a retirement of two-plus years about 10 days earlier, Donald didn’t travel to Australia.

With eventual partner in crime Myles Garrett watching from a suite after being placed on injured reserve with a knee injury, Donald notched three tackles, one for loss. While he didn't generate a quarterback pressure, Donald helped the Rams nearly double their pass rush win rate from the previous week simply by lining up, as his coach saw it.

"He elicits attention," McVay said. "He brings everybody up around him. And I didn't think it was by coincidence that the energy that we played with [tonight]. I thought really the defensive coaches did a great job with their game plan, but ultimately just elevating situations he's in and people that he's around and that's what the greats do and that's what he does."

With Garrett likely to miss at least the next three games while recovering from arthroscopic knee surgery, Donald must continue to adapt around LA’s other talented pass rushers.

Working through more double-teams than he would with Garrett around doesn’t quite scream “Welcome to the NFL” for a veteran of Donald's accomplishments.

If Donald still is up to it, though, imagine how the Rams might look in another month.