When Sachin Tendulkar takes a leg stump guard, he is up against the bowler, opposing team and, more significantly, himself. Batsmen are taught to play the ball not the bowler and to construct their innings according to the pitch and match situation.
That is okay for a normal player but Sachin defies the theory. Like a golfer who is hitting a stationary ball and playing the course, Sachin's batting is a battle against himself. The Master has repeatedly said he is not stressed by what fans or the country wants, the only thing that matters is whether he is able to meet his expectations and achieve targets. Sachin considers records as mere statistical milestones that will happen provided he remains hungry and competitive.
This formula does not work for others less gifted. For them, cricket is about fighting opponents who are busy plotting their downfall, also an inner struggle with self-doubt, uncertainty and insecurities.
This is why mental strengthening coaches are is business - the experts insist cricket is played more in the few inches between the ears than on the 22 yards. Physical training in the gym, hitting balls at the nets, watching DVDs of opposition bowlers and visualising, etc is fine but, at the end of the day, it is about each player's confidence level.
If the mind is weak, it shows in indecisive footwork and tentative strokes. For a batsman with an uncluttered mind and without internal demons, for instance, Virender Sehwag, the ball automatically finds the middle of the bat. Of course, reaching this state of confidence is far from easy. Every cricketer understands the need to focus on what is in his control, not fuss about the pitch and umpiring and other externals he can't do anything about.
Pressure never disappears but with experience players learn to handle it better. A young player might just ignore pressure and play with a no-fear attitude but someone on the road for a while tends to embrace caution and cut out risks. Youth has a point to prove; seniors have a reputation to protect.
Interestingly, there is pressure from colleagues and team mates as well. Players are fighting for a place in the eleven and competition from the bench waiting to get a chance can be a major source of stress.
Players often talk of fatigue/burnout and breaks to recover energy but nobody really wants to rest. Case in point: an injured Yuvraj Singh missed a game and lost his place to Suresh Raina who seized the opportunity by scoring a hundred on debut.