If you're a Bears fan who puts much stock in Pro Football Focus' grading system, then you're not happy with a few of the performances in the season-opening loss to the Los Angeles Rams.

PFF grades much like coaches might, although it's difficult to convince anyone they don't have their own agenda when some players often show up with high grades after what the naked eye could determine is a poor game, or vice versa.

Still, it is an independent alternate view of game performances off of film and it determined Danny Trevathan and Eddie Goldman might actually be a little more valuable to the Bears defense than some may have thought.

Trevathan's backup, Alec Ogletree had a team-low 29.1 overall PFF grade and 29.8 coverage grade at inside linebacker against the Rams.

Bilal Nichols, who had to play some at nose tackle because of the ankle injury to Goldman, came in with a 37.8 overall grade and a 40.4 against the run on a night when the defense did a respectable job of stopping the run with 74 yards on 23 carries.

The breakdowns in the Bears secondary weren't all Eddie Jackson's fault, according to PFF. He scored a 52.5, higher than both cornerback Kindle Vildor (48.9) and slot cornerback Marqui Christian (29.7).

Surprisingly, Robert Quinn had the best score among defensive starters with a 68.4 grade and 66.5 pass rush mark. Quinn had only two sacks last year but split a sack Sunday night with Akiem Hicks, who had a 76.4 pass rush grade but only 54.9 overall.

Khalil Mack, who last year graded out as PFF's best edge rusher with a season score of 92.5, had a 61.7 overall against the Rams.

The lowest offensive score by a Bears player was by left guard Cody Whitehair with a 37.4, including a 14.6 mark as a pass blocker. This isn't surprising since he had to go up against Aaron Donald.

A score that might surprise considering the amount of social media criticism he gets is Andy Dalton. PFF gave him a mark of 69.6, highest of all Bears on offense who started the game. Marquise Goodwin (73.0) and Damien Williams (72.7) had high offensive marks among key reserve contributors.

One thing to watch in the future is how much rest the Bears can get for Mack. He played 85% of the snaps with a slight groin injury, a season after he had 84% of snaps.

Coach Matt Nagy has made a point of saying he wanted to build in more rest for some of the older players, and Mack isn't old but is 30 now.

Twitter: BearDigest@BearsOnMaven