Well, that sucked. The Eagles not only lost to Washington, but ended any hope of making the playoffs even in the miserable NFC East. Yes, there’s a game left against the Giants next week. But it’s time to start looking at the bigger lessons of this season as well as this game.

1. Cutting DeSean was not the problem.

It’s amazing how many people keep repeating that the Eagles “miss DeSean” or “got nothing in return for him.” He’s simply not that good, and Washington is going to cut him after this year too, also getting “nothing in return for him.”

He’s an aging, one-dimensional receiver with a poor work ethic who’s only asset — speed — is the one that is most hurt by age. Unlike, say, Larry Fitzgerald, he’s not going to work on his game in the off-season to develop new skills that offset his natural slowing.

His heart is not really into it, which is why he skips non-mandatory workouts and spends his time on partying, music and his reality TV show. There is no better example than the pass he caught at Philadelphia’s 43-yard line with 4:35 left in the first quarter. DJax caught the ball in the middle of the field with room to run, but as Malcolm Jenkins closed he ran backwards three yards, then literally cowered as he gave himself up before the safety could tackle him.

DeMarco Murray was rightly slaughtered for sliding on a run to avoid getting hit, but if you criticized that, you have to do the same for Jackson — whose team was trailing in a game to clinch the division title at the time. At least Murray didn’t run backwards to avoid pain.

Jackson had a career year under Chip Kelly in 2013 — the only year he’s played all 16 games since his rookie year in 2008. But his production has been dropping since, from 1,332 yards to 1,169 last year. With his (somewhat vague) injuries this year, he’ll be lucky to top 500 yards, and he hasn’t returned punts well since 2011.

Fans like to say he opens up the run game as a deep threat, and his absence has been killing the Eagles run game. But Washington is 18th in the NFL in rushing this year, even with RB Alfred Morris and a much-improved offensive line. For all its problems with DeMarco Murray and the OL this year, the Eagles were much better running, 11th overall with 1,623 yards to the Skins’ 1,420. After signing DeSean, the Skins’ rushing yardage dropped a ton, from 2,164 yards in 2013 to 1,691 last year and 1,420 in 15 games this year. So, no. DeSean doesn’t help the running game.

2. Billy Davis has to go.

The Eagles have a lot of talent on defense, from one of the league’s best front lines to a much-improved secondary. For all the criticism of Chip Kelly as a GM, his acquisitions of Eric Rowe, Walter Thurman Thurmond and JaCorey Shepherd were home runs.

Even so, the Eagles have been killed on defense this year, giving up 394 yards per game — worst in the NFL.

I’ve been pushing back against the often kneejerk criticism of Davis, but something is clearly wrong here. Linebackers are lost and not improving, the defensive line is erratic, and Davis can’t seem to game plan for obvious opponent strengths, such as Arizona rookie RB David Johnson or Washington TE Jordan Reed.

3. Chemistry is a rare and valuable thing.

Good players don’t always work well together — DeSean Jackson was much more effective with Mike Vick than Nick Foles, and Mark Sanchez looks lost with any receiver not named Jordan Matthews.

This was especially obvious on the offensive line this year. Chip was wise to cut Todd Herremans, who was benched after two games in Indianapolis, and cutting Evan Mathis was at worst debatable. Jason Peters criticized Mathis very publicly for skipping Organized Team Activities last spring, and this I think forced Chip’s hands toward cutting Mathis, who lined up next to Peters on the left side.

But talent isn’t enough to make someone fit on an OL — there is a lot of communication and cooperation required. As talented as they may be (which isn’t very), Allen Barbre and Matt Tobin have just not fit in very well with the Eagles’ front line, and all of the team’s offensive struggles start with that failure.

Worse yet, Jason Peters at left tackle is old and fading fast. The Eagles now face the need to replace two or three starting linemen, and the risk of bad chemistry starts all over again with each one.

4. The Eagles won’t be very good next year, either — with or without Chip.

This team had a lot of very serious holes in talent that Chip (and before him, Andy Reid) have been able to mask with clever play-calling. Notably, the OL was aging and fading, the inside linebacker corps was weak and the secondary was abysmal.

Well, others teams have caught up with the play-calling and are exposing these gaps. There are too many to fill with the team’s draft picks, and last year’s experience shows the limits of high-priced free agents in building your team. The very cheap Walter Thurman was a great bargain, and Ryan Mathews proved to be solid value, but DeMarco Murray was a disaster and Byron Maxwell remained a good #2 CB without ever growing into the shutdown, follow-the-opponent’s-star-receiver type of corner he was paid to become.

This situation might improve as Chip Kelly learns the GM ropes, but the Eagles will need years to build up to a strong playoff team. Chip learned the hard way last spring why other teams don’t make a half dozen or more major roster changes in a short amount of time. Each change is something that can go wrong, and rapid-fire change without careful consideration of chemistry leads to, well, the awful season the Eagles are having.