I've seen Bill O'Brien happy.

I've heard the Texans' coach laugh so loud his echo fills up a room.

I've watched him joyously celebrate with so much enthusiastic pride that his 46 years fell away and a sports-obsessed kid from Boston was instantly brought back to life.

But I've never seen O'Brien go full roar, full blast like he did late Monday night in Cincinnati.

There was O'Brien, surrounded by fiery Texans still in uniform, inside the opponent's locker room at Paul Brown Stadium.

Then there was O'Brien, arms raised, cap in one hand, the other a clenched fist, shouting toward the ceiling after the once-undefeated Bengals were silenced, a 10-6 victory by the road team became an indisputable fact and the biggest win of his two-year career could never be taken back.

"Hey! Hey! Hey! Hey!" screamed the Texans, as J.J. Watt and Whitney Mercilus bounced around, and lesser-known players normally yelled at by O'Brien intentionally chest-bumped their coach.

"Ha, ha, ha!" proclaimed O'Brien, exhaling eight previous games filled with mostly fury and frustration, then calling the room to attention after the unified dance was complete.

The buzz kept going. Then the message was delivered.

"I couldn't be more proud of this team," O'Brien said. "But look, this is what we're capable of doing. … We just came in here on the road and beat an 8-0 team. And you ought to be (darn) proud of yourselves, because you worked your (butts) off. And you know what your reward is? You can wear sweats home!"

Eruption.

Blue, red and white-clothed bodies engulfed their coach. The room became a single extended shout, as jumping Texans briefly made their leader disappear, turning a pro locker room into a college party doubling as a Super Bowl celebration.

Roller-coaster ride

Monday's joy was two months in the making for O'Brien's Texans. And in a single game that could define a season - if the AFC South keeps stinking and this year becomes as crazy as it's setting up to be - we were reminded why we believed in the hot-tempered, always all-in coach in the first place.

Because he can coach.

Twice, O'Brien has been backed up against a wall, stripped of his weapons and been forced to survive with a season on the line.

He's a perfect 2-for-2.

And just like when O'Brien coached the heck out of the Texans in Week 16 last season, calling once-discarded Case Keenum out of a deer blind to miraculously shoot down the then 9-5 Baltimore Ravens, O'Brien rediscovered his best athletic attributes just in time for the Bengals on a national stage.

No Arian Foster and no real running game. Ryan Mallett discarded. A concussed Brian Hoyer. T.J. ("I was golfing three weeks ago and you cut me a year ago") Yates as O'Brien's third quarterback this season and sixth in 14 months.

And somehow, despite just 256 Texans offensive yards, O'Brien's squad gutted, toughed and clawed out the coach's first signature win of his pro career.

"Anytime you go into a game like that and you're playing an 8-0 team and you end up coming out on the winning end of it, that means a lot for your team," O'Brien said Tuesday at NRG Stadium. "Now, the key is for us that we have to understand how we got to that point. And the way we got to that point was we were honest with each other."

Let's be honest about O'Brien.

We're still figuring him out. Owner Bob McNair is, too. The good has been encouragingly good, the bad has been weirdly and embarrassingly bad, and what we're left with after 25 games is 13-12 O'Brien and a 2015 team that has a shot to make the playoffs (thanks to the wonders of the AFC South).

And only if the Texans play with passion and guts.

Winning cures all

For a myriad of reasons that ultimately are now just a fact of life, the Texans hadn't been right this year. They weren't in Week 1. They were a disaster in Atlanta and Miami. It took their everything just to beat Tampa Bay, Jacksonville and Tennessee.

But that team we saw Monday in Cincinnati?

It had the same heart of the squad that was 4-5 entering the open date in 2014, then rolled off five strong wins in its last seven games to come a quarter away from feeling the power of the postseason.

O'Brien inspired and guided that team. And his Texans sure as heck didn't quit on him on "Monday Night Football," even after Hoyer was hit so hard he couldn't remember the plays and 99.99 percent of the country had picked the soft-haired redhead from Katy with a shaky BB gun.

Rumors. Drama. Front-office intrigue and backdoor power plays.

You know how you burn all that away in the NFL?

By winning. By a coach coaching and a team playing like their lives depend on it.

O'Brien got his fire back Monday. He had to have recaptured McNair's eye.

Keep this crazy thing going in the season of no (Andrew) Luck and who knows where the Texans will end up?

It has been a while since they danced in January.