In a nutshell, here are seven main reasons why games are lost:
Turnovers - Bad Decisions
On offense, every possession must be valued. The goal of every possession is to get at least one good shot (and maybe more if we attack the offensive boards)... but at least one good shot (or two free-throws) each trip up the court. Notice that I did not say that we will score each time, because that is unrealistic. But we must value each possession, protect the ball, and get a good shot... each trip. Various violations (traveling, 3-seconds, illegal screen, etc.) and bad passing get in the way of achieving our goal of getting a good shot. Making bad decisions with the ball leads to turnovers and bad passes... e.g. dribble-penetration into two or three defenders, forcing a bad pass into the defense, etc. Have you ever watched an NBA or college game where a team fails to score for a long time? Usually it's not because of just poor shooting... it's turnovers, poor offensive execution, and poor shot selection. So... get a good shot each possession!
Bad Shot Selection
If you take a lot of contested shots, forced shots, off-balance shots, etc, your shooting percentage will plummet. Good defense can force you into bad shots as players become impatient and try to force the issue. And then there is the occasional player who is only concerned about his point total that game... but let's forget him for now. Throughout the season, in practice, define for your players what is a good shot and what is a bad shot.
What is a Good shot?
1. The shot must be expected by your teammates.
2. The shot must be able to be rebounded by two of your teammates.
3. The shot must be able to let our defense have a chance to get back in transition after it is taken.
4. The shot must be a high percentage shot for the shooter taking the shot.
5. The shot is dictated by time, score, and situation.
Let's look at the last one, #5 above. Jacking up a 3-point shot early in a possession, late in the game, when you have the lead... is a poor shot, even if it luckily goes in. It would be better to run some time off the clock, get a high-percentage shot or get to the free-throw line. In this situation, most successful teams will either get the ball inside to their best post player, or have their star perimeter player attack his defender off the dribble. Get inside or get to the line!
The 3-point shot is an important part of the game. But shooting a 3 every trip is not high percentage basketball. A 3-point shot taken with a defender flying out at the shooter is not a good shot (a shot fake and drive would be better here). So when is a 3-point shot a good shot? It's a good shot when your best shooter gets a wide-open look... or when a guard dribble-drives and then kicks the ball outside for a wide-open shot... or on a skip-pass where the shooter is wide-open. A 3-point shot in transition can be a good shot as well, unless we have a slim lead late in the game (as discussed above).
Forced shots inside are not good shots either. How often I see younger post players get an offensive rebound, only to throw it back up, contested, or off-balance and not squared up to the hoop... it's like the player thinks, "I got the rebound so I get to shoot it again." A much better play would be, if the put-back shot is not open, kick it outside to a perimeter player, who may be wide-open for a 3-point shot, or at least re-start the offense and, if you are leading, run some more time off the clock.
Dribble-drive and dish or kick-out is great offense and difficult to defend. But dribble-driving into a crowd and forcing up a bad shot is bad basketball.
Passing up a good, open shot is not desirable either, unless you are trying to run time off the clock. Sometimes a player will pass up a good shot, and then a bad pass or turnover occurs, and we get no shot at all.
Lack of Defensive Pressure, Lack of Hustle
Tough defense and rebounding will win most close games for you. I saw a high school team win a state championship a few years ago mainly by their great rebounding and defense... they could score too, but were only a little above average on offense. As we said above, on offense we want a good shot every possession. On defense, we want to contest every shot and pressure the ball. Keep the ball out of the paint. Force a bad shot, bad pass or a turnover... and then get the rebound. It's one shot (contested) and OUT! Great defense will win those games when your offense is struggling... and you can play great defense every game. No player should ever rest on defense... not even for one possession. If you need to rest, rest on offense... or on the bench. Poor defense, giving up easy shots, failing to hustle after loose balls are major causes of losing games.
Not Blocking Out, Not Rebounding
To reiterate... tough defense and rebounding will win most close games for you. It's one contested shot (contested) and OUT! No second and third shots... if you fail to block out and rebound and give up extra shots, your chances of winning are greatly diminished. When you are on defense, you must have that mentality of wanting to get the ball back. As soon as the shot goes up, everyone blocks out and rebounds. Failure to block out also results in more fouls... the offense gets the rebound and we foul on the put-back attempt. In my experience, if you lose the rebounding war, you will probably lose the game.
Can little guys out-rebound a bigger team? It's hard, but if everyone is aggressive in boxing-out their man away from the hoop, it can frustrate the opponent, and instead of working to get around your box-out, they may start pushing in the back or going over the top... which may get their "bigs" in foul trouble. Boxing-out is a foot war... quickness counts.
Not Getting Back Defensively
Failure to sprint back on defense, i.e. poor defensive transition, results in easy shots and lay-ups for the opponent. Sometimes players don't sprint back because they are tired... take a time-out, or rest the player(s) on the bench for a couple minutes. It's an amazing thing, but sometimes players think they are sprinting back, and then we show the game film the next day, and they realize that they could be quicker. A key here is the first two or three steps... often a player will see that the opponent has gotten the rebound, will hesitate for a second or two, and then decide to run back... often too late. Players must learn to immediately recognize the change of possession and make those first few steps quickly. Many coaches teach players to run back to the paint, with one player stopping the ball, and the other four players getting one foot in the paint, and then fanning out to pick up the ball or their man from there.
We have a rule on sprinting back... whenever the ball is even or ahead of you going up the floor, you had better be in an all-out sprint to catch up, or we'll assume that you are tired and need a rest on the bench! But what if my best player is not getting back? Well, he may not really be your best player, or he's tired and needs a rest. Great players want to win and compete on both ends of the court.
There are good fouls and bad fouls. Fouls in the back-court (i.e. in a press defense), or 80 feet from the basket (i.e. fouling the rebounder) are usually stupid fouls. The game (and the clock) stops. If in the double-bonus, we walk down the floor and they shoot two uncontested free-throws. You may have to do this late in a game if you are behind... but otherwise, these are dumb fouls.
Fouling the jump shooter is usually a bad foul. Get a hand up, but don't foul... and block-out. Reach-in fouls on the perimeter are not good fouls... instead players should learn to move their feet and get help from teammates on dribble-penetration.
A good foul may be fouling a lay-up or an inside, high percentage shot... these shots must be contested, and occasionally you'll get a foul... that's just the way it is. We don't intentionally foul in this situation, and never want our player to take a "cheap shot" at an opponent going in for a score, but we do want to contest that shot.
Bad fouls early in a game get your players in foul trouble, and then they have to sit. Late in a close game, as your team's foul total builds up, the opponent gets to go the free-throw line and score easy free-throws without taking any time off the clock.
Failure to Play as a Team
If one or two players are just playing for themselves and their own "glory", many of the above-mentioned factors come into play. Bad, forced shots are taken. Attitudes develop and players stop hustling and working hard on defense. Your "star" players may not sprint back on defense, and may loaf of defense. Selfishness results in poor passing and cutting. Players may get angry when taken out the game by the coach. A negative attitude develops on the bench and players are not pulling for and helping each other. Coaches start yelling at their players, and the refs.
A team with twelve or fifteen players playing hard together as one is a tough team to beat.
Your "star" players must realize that when the all-conference honors and awards go out at the end of the season, most of those awards go to players on winning teams... not just good individual players... just another way of selling the "team" concept.