I reacted to this aswell when the defender was dribbling around. It is one of the main causes why the game feels too fast. Most animations and movements are not unrealistically fast, but the base movements are way too quick and fast. Like you say, it doesn't feel like the player slows down, and if he suddenly stops and goes in the reverse direction, it looks almost like he is being pulled by some harness and invisible string. There is nothing in those directional changes that suggests the movement is coming from the players legs and feet touching the ground.
Also, and I am not sure anyone has realized this, but if you take a player in possession of the ball, and a player not in possession of the ball, certain moves are actually faster when performed by the ball carrier, and some are equally fast. Logically, manipulating the ball would slightly hamper your speed compared to the same player doing the same kind of movements, but not having to use his feet to move the ball around.
A good example is jogging and turning 90 degrees. A player not in possession will do a realistic animation where he needs to push off into the new direction. A player in possession just dinks the ball into the new direction and is just pulled along, with almost no loss of momentum.
YouTube - MOV00008
When you look at the video, and just look at the player movements, ignore the ball, doesn't it strike you as terribly inconsistent? And this is the World Cup game, or FIFA 10.5 as far as gameplay, I suppose. Players in possession are treated completely different, and alot more favorably, with regards to the physics of movement than off-the-ball players.
I don't see why this movement scheme still seems to exist, since it is one of the big reasons why dribbling and speed is king. The same player with the ball can move alot quicker than the same player without the ball. On-the-ball movement should be based on the off-the-ball movements from the video, and then slowed down slightly more to be realistic.