defensive tackling

i am having trouble tackling when i hit circle to change my player closest to the player with the ball it seems the cpu gives me a player thats way out of pursuit...can some one give me some help with this or else i am doomed

thanks

hmm dont realy know i change player and got the one closest and then i hit them hard!

My guys still slow down if I click B to grab a new guy, that kind of pisses me off.