Johnny can score big, but who plays the D?

          The main obstacle that stands in the way of the Alabama Crimson Tide winning its fourth national championship in five years is the precocious, outrageous, out of control kid with out of this world talent.

You know him as Johnny Football.

He is in fact Jonathan Manziel, and his fascinating good-bad-and-ugly story is told in detail by Mark Roberson elsewhere in this sports blog.

What I’m doing here is previewing the most anticipated game of this young college football season.  It’s No. 1 Alabama against No. 6 Texas A&M, which has one of the most decisive home-field advantages in North America.

The Tide rolls into quaint little College Station to face not just a highly talented 2-0 team but a crowd of 86,000 that will be as vocal as any, and standing most of the time.

Don’t believe the theory that Aggies are so disgusted with Manziel’s misbehaviors that their enthusiasm is dampened.  This is the first time their school has contended for a national title. That totally overrides any misgivings about Manziel’s drinking, carousing and autographing binges or his too-hasty tweet that he looks forward to leaving A&M.  The vitriol against Johnny has been so loud it almost makes him a sympathetic figure.

The fact the Aggies won on Alabama’s field last year, 29-24, has to give them confidence they’ll win on their own.  Other colleges promote the Twelfth Man concept, but it does seem more a reality at A&M than elsewhere.

Alabama’s coach Nick Saban does not try to tug emotional strings, at least not overtly.  He’s all about man-on-man football, applying his team’s unique advantages in speed, strength and depth to win the individual matchups.

Bama’s players are not talking about revenge for the only defeat they suffered last season, although Saban is 15-2 against teams that have beaten him in previous meetings.  Wide receiver Amari Cooper, a legitimate All-America candidate, pointed out that Alabama and A&M have changed considerably since 2012.  Bama lost nine starters, Ags11.

“If you lose a fight with someone,” Cooper said, “you don’t get revenge from fighting someone else.”

While the methodical, if not robotic, Saban downplays emotion, that is a key element of the Aggie tradition.  Manziel fits it perfectly:  “I’m just an emotional player with my heart on my sleeve.”

Prior to the previous game against featherweight Sam Houston State, Manziel addressed his teammates, professed his love for them and apparently pulled them all together, just in case some were alienated by his various shenanigans.

Yes, if you take emotion out of it and the game comes down to physical ability, Alabama wins handily.  But even here the teams may be closer than you think.

In a misleadingly lopsided 35-10 victory over Virginia Tech in its opener, Alabama’s offensive line, with three new starters, did not block well.  The Tide totaled 206 yards, had 11 negative plays.

And while A&M was underwhelming in victories over Rice and Sam Houston, what’s overlooked is that Aggies coach Kevin Sumlin approached those two games as preseason.

He was preoccupied – as was everyone around him – with the Johnny Autograph circus.  Sumlin used the first two weeks of the season to establish discipline and develop a winning mentality heading into Armageddon.

The coach suspended four of his starting defensive players for the two games, for violating his rules.  It’s hardly surprising all the suspensions ended in time for the chastened athletes to face the Tide.

The point is, the Aggie defense that plays Saturday (2:30 CST start on CBS) will be much better than the one we’ve seen so far.

Though it’s fair to ask if it’s good enough.

Charles Ross of underrated Rice, who’s hardly the equal of Alabama’s TJ Yeldon, battered the Aggies’ front.  Then again, Ross might have found it hard to push aside one of the suspended starters, Steven Jenkins, senior linebacker who last year had 79 tackles, 5 ½ for losses, while also knocking down three passes.

Jenkins’ excellence notwithstanding, Alabama has the better defensive line and linebacking.  But those advantages could be offset by the Aggies’ superior offensive line.

A&M has two 6-5, 300-pound tackles, Jake Matthews and Cedric Ogbuehi, who are projected first-round draft picks.  They’re likely to stymie Saban’s efforts to apply outside pressure to confine the elusive Manziel to the pocket and beat him into the ground.

The teams may be fairly equal in the secondary, which is considered the Tide’s weakest defensive unit.

Alabama has better receivers and running backs, but A&M has lots of good ones.  The point here being Manziel can expect solid protection and enough of a running game to keep Bama off balance.  The Heisman Trophy winner is likely to have more success throwing than Alabama will have.

“I’m a lot better passer now than I was a year ago,” Manziel said, before – under advice of lawyers — he stopped talking to the media in the run-up to this game.  His claim has been confirmed by some coaches and NFL scouts who have seen his recent play.

AJ McCarron of Alabama is a fine quarterback in his own right, but he’s not nearly as electrifying as Johnny Football.  Think of Manziel as a compact Colin Kaepernick and McCarron as Alex Smith.

Saban has said his most troubling challenge in devising a defensive scheme is an improvising quarterback.  Manziel is one of the great improvisers ever.

And in Sumlin, Saban faces an adversary who may be his equal as a strategist and tactician.  Although Sumlin is most known for his mastery of the spread offense, no coach in the country, pro or college, is more respected for his knowledge of defense.

When the Green Bay Packers coaching staff last spring wanted to learn how to defend the read-option, they visited College Station.

Saban, though unquestionably the most dominant college coach of his generation, can be annoyingly pompous.

Prior to the BCS title game in 2009, he treated the Texas Longhorns as an afterthought and even expressed it in a speech to his players.  He compared Alabama’s season to the U.S. Hockey Team upsetting Russia in the Lake Placid Olympics and then going on to knock off the much less significant Finland before capturing the gold medal.

“Florida was Russia,” he said. “Texas is Finland.”

In other words, you win the Southeastern Conference, you’re automatically the best there is.

And at least in this case this year he may be right.  No doubt the winner of this game will emerge as the heavy favorite to win the national championship, though the Pac 12, with Oregon and Stanford, will have a say, as perhaps will Ohio State of the Big Ten.

Alabama is favored by more than a touchdown.  The betting line is selling short A&M’s O-line, the inventiveness of Manziel and Sumlin and the Category 5 force of a vibrating, thunderous Kyle Field in the most significant game it has ever hosted.

Crowd emotion can’t make players run faster or execute plays better, but it can cause a so-so defense to hit harder and play with more intensity and stamina, especially in the trenches.

Look for lots of spirit, magical offensive plays, touchdowns and drama.  I give the nod to Alabama, not the least because of its tremendous special teams and the Saban-enforced discipline.  But this should be a very close game that lives up to its hype.