Much slower frame rates in 1 on 1 mode than in a real game

I have a 128 Mb Nvidia Geforce 6200 and when i run my game, i can take it all the way to max settings and be able to play a 5 on 5 decently. But when i go to play a 1 on 1 or a practice mode, it is considerably much slower in frame rates whenever there is fast motion in the screen(like when i shoot the ball). I tried everything, from lowering my settings to the lowest, turning off lighting and vsync, but still it does not make any difference from whatever setting i have, it all turns out just as choppy.

Here are my specs:

128 mb Nvidia Geforce 6200(6 series)
Windows 2000
1 GB Ram
AMD Athlon(tm) XP 3200+, ~2.2 ghz

There's got to be an answer. I'm pretty sure it ain't my graphic card but the settings or maybe a driver compatibility.

Screen resolution you are running it on? Sometimes the higher, the slower...

I tried lowering the resolution. Overall it was faster, but that didn't solve the problem of why the frame rates get choppy when there is speed involved in the scene, like when i pass or shoot the ball from a far.