1. The mind and body are connected.  All of the physical skills and superiority that your players have is marginalized if there is not also good mental conditioning as well.
2. Negative mental chatter is one of the leading problems affecting physical performance.
3. To limit the chatter, practice some form of meditation (doesn't have to be in a Buddhist hall!), practice pressure situations (3rd and 10 in the red zone with crowd noises with something at stake for the team like sprints), and minimize individual egos through team building exercises. 

Mental Chatter Affects Performance

All of your skills, your motor functions, your hand-eye coordination, your split decisions...everything in sports is controlled by the brain.   When the brain is chatty and negative, it throws off your game.

Your body obeys dual voices from your brain.  One of the voices is the strong silent type.  Your body carries out quiet instructions from the brain.  When this happens, you usually play in the zone.  The other is a chatty, negative voice.  It's parental, like a strict father.  It's never happy, and it lets you know it.  It degrades you, globalizes negative events, is shallow and sensitive.

Think of the process of trying to make a tackle in football.  A very stern internal voice is barking at you for missing the last tackle.  When you see the ball carrier come your way again, you get nervous.  Fear, rage, embarrassment, sadness, envy, hope, disappointment -- all muck with your nervous system.  You start thinking 'what if I miss' and other nasty thoughts.  The mind is not quiet, and the body gets tight.  It stiffens muscles that should be lose and makes you rush your tackling sequence so that you're out of step.  As a result, you do in fact miss.  Then you generalize ('I'm not a good tackler") and maybe even globalize ("I've never been good at anything"), and then you're done.

However, in reality, nothing has changed.  You're still the same good player who has put in hours of practice, who knows what to do if the mind would just be quiet and get out of the way.  What went through your head are just thoughts, and thoughts are not real.  Just because you think something doesn't mean it’s important.  Thoughts are like whispy little clouds, and you are a mountain.  You get to analyze whether they're real or not, and the more you look at your thoughts, the more you'll realize that your brain sometimes acts like a spoiled little brat.

The best way to stop the chatter, to quiet the mind, and to increase focus is meditation.  The idea of sitting a football team down on a field in full pads in a cross-legged position chanting 'ummmm' is not very practical, but there are other ways to implement it off the field in small groups and in daily activities that make it extremely practical.  Call it 'mental fitness', call it 'mental conditioning', whatever it takes to get self-conscious athletes over the hump, but meditation is one of the best tools you can teach to allow players to quiet their minds.  As a meditative practice, wherever you are, simply observe the breathing process for five minutes or more. Do not force your breathing, observe it without interfering. Whenever any thoughts arise that distract you from your focus, let those go, and gently return your attention to your breath. Return to your breath as many times as you are distracted. With practice, this will become a means of entry into a quiet mind and athletic flow.  Players can do this in the car, standing in line, any time a moment comes available.  

A second way to reduce the chatter in your head is to practice pressure situations.  Practice makes things routine, and routine takes away the pressure.  You can also reframe situations from a pressure event to a fun event.  When you practice pressure situations, make them fun and entertaining, not derogatory statements on the team and the player.  For example, at the end of practice, we sometimes base the amount of sprints on whether our kicker can make a 'game-winning' field goal.   This puts enough pressure on him to let him practice the real thing without things getting too nerve-racking.  On 7 on 7 drills, we keep track of how many touchdowns would have been scored if it had been a real game.  Just the very fact of keeping score brings out a fun, competitive spirit while at the same time raising the level of pressure.

As a coach, I try to minimize pressure before game time.  You often hear clichés from coaches about 'raising the bar', 'play 150 percent', 'step up your game.'  I tell my players the exact opposite.  I tell them to just go out and play their regular game. If we're in a pressure-filled situation like the playoffs, we're there for a reason.  We're probably pretty good at this game.  Go out and play like you would any other day.  You've already trained yourself to perform.  Like walking or riding a bike, you don't have to pep yourself up or think about doing these activities.  Just do what you already know how to do, one play at a time, and the winning will take care of itself. 

A third way – minimize ego.  When you play with ego, you increase your stress.  Every play, every point, and every mistake is a statement of your identity.  There are times you will shine and your ego will expand, but for the most part, you live in fear -- fear of missing a tackle, dropping a pass, or letting down yourself and your teammates.  Ego lives off of comparison, and it is often a harsh critic.  Ego is a roller coaster of hope and fear, and it's not a very fun ride.  

One way to minimize ego is to place the team front and center.  Most players join a football team to experience something larger than themselves, to achieve goals that they couldn’t do alone, and to feel a sense of camaraderie with their fellow teammates.  Give them what they’re looking for by planning events that build team chemistry. 

Another way to deflate ego is just to observe it, like a scientist looking at an experiment.  When you think something like "I'm not good at this" you don't have to believe it.  Instead, just label it 'thinking' and observe how it tried to wrap your mind.  You'll soon see that your thoughts are not as sophisticated as you once thought.   If you need to analyze your performance, stick to the facts.  Don't say to yourself "I'm awful at open-field tackling."  Say "I missed the last tackle."  The first statement is an opinion, the second one is fact.  Stay with the facts, because the ego is a master at deception and distortion when it comes to opinion.

Quiet the mind through meditation, practice pressure situations, minimize ego and build the team – all of these techniques get the brain out of the way to let the body do what it already knows how to do.

Because the brain needs more than air to operate at a peak state.  It needs the right fuel and rest to run effectively.  If you're not giving it these basics, you might as well not train at all.

Test your nutrition knowledge at http://psychologytoday.tests.psychtests.com/take_test.php?idRegTest=1319.