When you settle into the sofa to watch football this weekend, you probably won't be crafting psychological profiles of the players as they go slam-banging around the field. But Dr. Bob Troutwine will.

Troutwine is a Missouri psychologist whose consulting firm performs psychological assessments of players for NFL franchises, helping them put together teams that are mentally as well as physically fit. Troutwine has worked for 17 teams since breaking into big-league sports psychology in 1984. During each year's college draft, he gives clients guidance on their picks by working up psychological snapshots of the various hot-shot players coming out of college.

Through one-on-one interviews and written tests, Troutwine draws a picture of each player's mental condition and leadership potential. "It's structural behavioral interviewing," he explains. "I dig for specific behavioral examples of what they've done in the past. I'll say, 'Give me an example of a time when you impacted another player's performance.'"

In one interview, a quarterback responded to that question with the story of how he affected a particular teammate -- a wide receiver who was slacking off during a game. When the QB saw the receiver jogging through his route, he went to the sideline and told the coach. Bad move, says Troutwine: "That's like running to mommy." If you're a coach, he says, you don't want that; instead, "you want someone who's going to be a leader on the field."

NFL teams eat up Troutwine's player assessments, but psychological profiles don't always provide an accurate forecast of future performance, says Andy Meyers, president of the Association for the Advancement of Applied Sport Psychology and chairman of the psychology department at the University of Memphis. "It's always been a dream of psychologists that we could use assessment strategies to predict performance," Meyers says. "But the historic evidence on these tests has not been impressive."

According to Troutwine, his results have been impressive enough to keep clients coming back season after season: "Believe me, you don't last 16 years in the NFL if you're not successful."

Peyton Manning is one of Troutwine's most memorable success stories. In the 1998 draft, the Indianapolis Colts had the No. 1 pick. They wanted to select a quarterback who would not only perform at a high level athletically but who would also fit into the team's close-knit, family-like organization. Troutwine helped the Colts settle on Tennessee's Manning over Washington State's Ryan Leaf.

"They graded out almost identically on physical attributes," Troutwine says, referring to the size, speed and arm strength of the two star quarterbacks. But Troutwine saw another kind of difference. "Manning had a lot more maturity -- mentally, emotionally. You saw a lower level of maturity in Leaf." Manning was more stable, too. According to Troutwine, "He's the kind of guy you'd have over for Thanksgiving dinner."

Troutwine's assessment has been dead on so far. Since the two quarterbacks entered the pros, Manning has become a reliable, productive player for the Colts; Leaf, on the other hand, who was drafted by the Chargers, has struggled with the team, alienating teammates and lashing out at journalists and fans.

Sometimes players with wildly different psychological make-ups can be equally successful. "Steve Young is like an accountant, Brett Favre is a rodeo star," Troutwine says about the perennial Pro Bowlers from San Francisco and Green Bay. "Favre is scary, but he makes things happen."

So, besides that elusive ability to "make things happen," what's the most important mental quality for an NFL player? "The ability to learn," Troutwine says. "In today's league, with the zone defense, a player has to make three or four reads right before the snap of the ball and three or four more reads after the snap. This all happens in milliseconds. So the most important thing is learning ability." After a beat, he adds, "Notice I didn't say intelligence."

Troutwine also ranks old-fashioned meanness high among desirable qualities for pro football players -- especially linebackers. But you can't really test for meanness, Troutwine says. "It's a complex trait. We look for a high level of personal drive. This is a very violent game. You've got to have a love of collision."

But for a pro sports team it's equally important that its players learn to control those violent tendencies once they walk out of the stadium, because bankrolling off-the-field psychos tends to mean bad P.R. for the team. "You can always find crazies who'll run down the field like maniacs," Troutwine says, "but can they switch it off when they're away from the game?"

When they can't, things get ugly fast. Troutwine points to the case of the famously unstable Alonzo Spellman -- the former Chicago Bear who in a string of well-publicized 1998 freak-outs barricaded himself in his publicist's home, kicked his way out of a psychiatric hospital, got divorced, got evicted and had several run-ins with the law before the Bears finally cut him loose.

OK, so Troutwine knows a gridiron psycho when he sees one, but the University of Memphis' Meyers puts the big question to Troutwine's brand of psychological headshrinking: Is this science? "The two key things in science are repetition and validity," Meyers stresses. "Can he show you 1,000 cases where [his assessments] worked successfully? Can he show you peer-reviewed, published evidence that his predictions work?"

Troutwine says that allowing peer review of his assessments would be like giving away money. "All our information is proprietary and competitive. We've discovered some secrets to athletic success, and we don't feel like sharing those." Besides, Troutwine says, his peer review comes straight from the top. "I consider the coaches, management and players my peers. Believe me, we get peer-reviewed very seriously every season."

As long as there are professional sports, Troutwine says, there will be a role for the sports psychologists who minister to stressed-out athletes. Playing week after week in the national spotlight takes a heavy mental toll on even the most level-headed pros. "Players tell me it's the psychological toll more than the physical side that gets them," Troutwine says. "There are no easy games in the NFL. Every week you're playing top-quality opponents. It's hard to be up all the time."

And when pro players finally retire or get knocked out of the league by an injury, they face yet another psychological battle. "The game has a seductive quality," Troutwine says. "When your career is suddenly over, you miss the admiration." In other words, selling used cars in suburbia just doesn't compare to plowing into the end zone to the screams of 70,000 adoring fans. "You miss the life," he says.

Meyers remains skeptical of the value of psychological evaluations for predicting performance, but he's willing to admit that Troutwine will rule the NFL as long as he keeps nabbing the right players for the right teams. "Can he do this repeatedly? If he can, he'll be a very successful guy."

Meanwhile, Troutwine hopes his NFL success will breed success in other pro sports leagues. In the near future he plans to diversify his business by moving into the National Basketball Association. So what's his opinion of the psychological state of a famously oddball NBA player like, say, Dennis Rodman?

"Oh, he's got everybody fooled that he's some kind of renegade," Troutwine says. "He's torn a page right out of the Muhammad Ali how-to-deal-with-the-media book. I wouldn't be afraid to have him on my team."