They're back (to being a total mystery)!

Eagles running back LeSean McCoy scores his second touchdown against the Cowboys. (Ron Cortes/Staff Photographer)

The Eagles are unstoppable. After Sunday night’s primetime humiliation of the Dallas Cowboys, we can all be certain of that much.

Just as we were certain the Eagles were unstoppable last November after Michael Vick’s epic performance against Washington on Monday Night Football.

Just as we were certain the Eagles were unwatchable after they blew three consecutive fourth-quarter leads earlier this season.

Say what you want about Andy Reid. In his 13th season as head coach, his team is absolutely unpredictable. These Eagles are capable of beating any team in the NFL, especially themselves. They can look inept and, well, ept in consecutive weeks. It’s as tough to get a handle on them as it was for them to get a handle on the football in Buffalo earlier this month.

A defense that couldn’t stop Buffalo or San Francisco shuts out the Cowboys. An offense that fizzled in the red zone and turned the ball over for weeks scores on its first six possessions. A turnover-prone quarterback is almost perfect in piling up a 24-0 halftime lead.

It wasn’t quite the once-in-a-lifetime performance Vick unleashed in that 59-28 romp over Washington last season. After that, Vick’s name immediately was included in every discussion about potential MVP candidates. Reasonable people wondered – out loud! -- whether it was possible for any NFL defense to stop Vick, DeSean Jackson, LeSean McCoy and the rest of them.

 Vick had finally married his breathtaking ability to a hardworking approach to preparation. Just like that, Tom Brady and Peyton Manning were yesterday’s heroes.

Except, of course, that Aaron Rodgers was the winning quarterback in the Super Bowl. Vick and the Eagles turned out to be quite stoppable, losing their final three games. The last was a playoff game against Rodgers and the Green Bay Packers.

The unstoppable Eagles became so stoppable, in fact, that Reid replaced his defensive coaching staff and made radical changes in the team’s approach to offensive line play. There followed a spending spree to infuse talent onto the roster.

Expectations spiked again, almost as high as they were after those thrilling wins against Washington and the Giants a season ago. Surely the Eagles had the talent to dominate in the lockout-hobbled NFL.

Then they were 1-4 and expectations had crashed through the floor again. Surely Reid would be  fired. Surely his decision to promote his offensive line coach to defensive coordinator was the final straw. It was as if every decision Reid made was a beautiful hand-rolled Cuban cigar, and every single one had an explosive charge in it.

So we knew they were great last year. We knew they were great this summer. We knew they stunk three weeks ago.

What do we know today?

Not much. We know Reid’s bye-week magic formula still works. He is 13-0 in the games after the Eagles’ bye. Considering the opponent and the stakes, and the sheer one-sidedness of it, Sunday’s may have been the most impressive of those 13 wins.

But does it mean the ship is righted? No more than that Washington game proved Vick had been transformed into a quarterback-god.

There are some similarities that might explain this. It came to light afterward that some of the Washington players had been talking trash to the Eagles before that game. They were thus inspired to inflict a beating so humiliating that veteran defensive lineman Albert Haynesworth said it looked like the Eagles were compiling “BCS points. They should be ranked No. 1 now.”

Of course, it was Dallas defensive coordinator Rob Ryan, in the grand tradition of his father, who offended the Eagles this time. Ryan called the Eagles “the all-hype team” and promised the Cowboys would “beat their ass.”

For those of us who remember Buddy Ryan’s “Greg Bell, my ass” quote before the Rams’ running back ran for 124 yards and a touchdown in a 1989 playoff game, this was especially amusing.

The Eagles may indeed be the all-hype team. Time will tell. But the scoreboard said Eagles 34, Cowboys 7 Sunday night.

The problem with this sort of motivation-by-perceived-slight is that you can’t rely on it week in and week out. There wasn’t any of this stuff in those boring seasons when Reid’s teams consistently won 11 or 12 games and went deep into the playoffs. Those Eagles were just professional, tough and determined to find ways to win. Yawn.

It is possible the Eagles have figured things out and are about to bark on a strong run to the postseason. The state of the NFC East certainly makes that possible.

It is equally possible that the Eagles will be terrific some weeks and terrible other weeks, that Vick will wear down as he did last year and that expectations will soar before crashing cruelly once more.

Mirage or shimmering pool of Super Bowl hopes?

Dive in at your own risk.