At times you may be shorter than the opponent you have to guard. What can you do to make up for this difference and what can you do to make take advantage of the difference.
Positioning, using your intelligence and out smarting the opponent are all ways to guard a taller and or bigger player.
Use your head. The best way to make up for the difference is use your smarts. Out smart the opponent. Use your intelligent to make up for the difference in size. For example when you are boxing out spread your legs wide to get a strong base and get low. The lower you are the stronger you will be. If you get low to box out and stick your butt into the opponent, this a lot of times will take him out of his game since he will feel your bottom on his legs and will cause him to be uncomfortable.
If they take you down low and post up on the box, you can first of all beat him to that spot and make him post up further out. If he beats you to the spot, then front him. Ask for weak side help from a team mate and front him so they have to throw over you and risk a turnover or even a charge. Another way to out smart him is to lean into him, not so obviously but let him feel your weight and if the pass comes to him, back away and he will lose his balance and many times travel or miss the pass.
On the wing
If the bigger opponent is a guard and he has you on the wing; if he has the ball then get in his face and use your speed advantage to your advantage. Most likely he will not be able to take you on the dribble so get up close to him and either lead him to where your team’s defensive strength is or lead him to the baseline to use the out of bounds as another defender.
Use your head
Chances are if you are shorter then blocking his shot is not advisable, it probably will only lead to fouls. If he shots put a hand in his face. Right up into his face if you can. If he dribbles, use your speed and agility and either steal the ball or make him turn it over. Usually the taller the opponent the less dribbling skills they have, use that to your advantage.
If the difference in size is extreme and the team finds it is just impossible to defend the opponent, then there may be the need to change defenses. A zone defense may be an easier way to lessen the opponent’s impact. This often happens if the best opponent is a post player.
The team can play zone and the guards can sag down and help double team if the ball goes down low. The disadvantage is if the opposing team has good shooting guards as well and you may risk that they will stick those open jumpers even the big man can kick the ball out since your team doubled down.