Ahhh . I wasn't going to do this, but...
It's true that a big part of shooting free throws is mental. But that doesn't mean that you can instantly say that Parker doesn't have the mental toughness he needs. When you are surrounded by a bunch of guys who are tossing up bricks, it becomes a lot harder to keep a mental picture of a free throw cutting the cords. Constantly being around bad free throw shooters will cause most players to begin shooting them worse. Don't believe me? Talk to any good golfer you know, and ask him or her how difficult it is to play with someone who shoots 110, and still turn in a good score. Some days you can block it out, but a lot of the time you can't keep it from dragging you down.
And free throws aren't all mental. You see a lot of bricks thrown up in the 4th quarters of games because of the pressure, but a lot of them are also caused by tired legs. Tim Duncan spends 100% of his time in the blocks with some huge guy leaning on him. Besides all of the normal running in a basketball game he is, in effect, doing 20+ minutes of leg presses every night. Does that have an effect on his legs, and do legs have an effect on shooting free throws? You bet. Here's a little experiment you can try at home: go and do a really heavy leg workout. Not the wimpy kind, like you usually do, but one that really fatigues your legs - makes them feel a little shaky. Afterwards, squat down and jump; you can probably do okay with that. Then squat down and try to stand up really slowly. That's a totally different story. Try shooting a few free throws while your legs feel like that. Then come back and talk about the mental aspect.
What makes it worse is that things begin to feed on themselves. Miss a few free throws, and it becomes harder to make the next one. A lot of the mental part of shooting free throws, just like making 4-foot putts on the golf course, is about visualing. Being able to see yourself make a good stroke, being able to see the ball go in the hole, before you let go. Miss a few, and it becomes harder to visualize anything but the ball bouncing off the rim. Miss a few free throws at the end of the game because your legs are tired, and you remember it next game. Golfers call it "the yips", and any sports psychologist will tell you that it is incredibly difficult to get past.
It seems kind of funny that the other 3 "premier" teams in the league shoot almost as bad, or even worse than the Spurs do from the line. Consider that maybe... just maybe... there may be reasons why the Spurs shoot FT's so poorly as a team. (I mean besides them being mentally weak and never working on them at practice.) I've always believed that the Spurs' brand of defense contributes, at least a little bit, to their lower free throw percentages.
There is some good news for the Spurs, too. Most of them are getting to the line more and/or shooting a higher percentage than last year. Bowen's FT% increased 55 points (5.5%) over last year, Duncan's increased 71 points, Nazr's increased 101 points, and Horry's increased 144 points. And, while Manu's percentage stayed the same (.803), and his minutes played decreased, he went to the line 442 times this season vs. 298 trips last season. However bad they are, the charity stripe is contributing a lot more for them this year than last year. And I thought they were about .4 seconds from having a really good team last year.