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The Titans lost both their quarterback and their playoff chances on Christmas Eve when Marcus Mariota went down with a broken ankle.

The fact they were that close underscores how solidly they’re built, and how close they are to making their turnaround real.

After solidifying both lines (their offensive line doesn’t get the publicity of others, but is among the best in the league starting with tackles Taylor Lewan and Jack Conklin), this offseason was spent adding skill position talent for Mariota.

While they might have surprised some by taking wide receiver Corey Davis fifth overall, they think he can be the kind of lead dog that group needs. Third-rounder Taywan Taylor also has some promise for a group that’s suddenly deep. Being able to pick up a solid veteran like Eric Decker late in the offseason was a gift, and should help Mariota balance things out offensively.

They’re not a particularly flashy team, such that a Mike Mularkey-coached team ever would be. But they’re nothing if not stable, and suddenly making people realize it.

Biggest positive change: The Titans were forced into too many shootouts last year, primarily because they were 30th in the league in pass defense.

So they made it a priority to add to the secondary, spending heavily on cornerback Logan Ryan and bringing safety Johnathan Cyprien in in free agency, and then using their second first-rounder on cornerback Adoree Jackson, who was one of the best athletes in this year’s draft.

They needed to make big changes there, and if they work out, it’s going to be harder to find weaknesses.

Biggest negative change: It’s hard to find one. Sure, they lost veteran tight end Anthony Fasano, but that’s not a deal-breaker.

If anything, they’ve lost the ability to surprise people, as they’re suddenly a trendy pick and getting more attention than they have in years.

Coaching thermometer: It ought to be absolutely frozen.

Mularkey might not inspire deep feelings among the fanbase, but his old-school methods have stabilized things there and are working.

Whether it works long-term remains to be seen, as his reputation with players is of a guy who can wear guys out (physically and mentally). But at the moment, it’s hard to argue with the job he’s done.

We’d like to crack a beer with . . . Mariota has everything you’d want in an NFL star quarterback except perhaps personality. It would be curious to know if there’s one lurking deep inside there.

Not every quarterback has to be Brett Favre (on or off the field), and perhaps his stoic demeanor is a thing to be applauded in an age where everything is hype.

How they can prove us wrong: If the grind of being a physical team wears on them more than their opponents, they could easily fade.

The AFC South, long a punchline, is deeper and more talented than it’s been, so it’s actually going to take some work to win the division this year. But if the secondary improves, if Davis fulfills his promise, and Mariota gets used to having more to work with, the Titans could become a threat for years to come.