Yeah, getting the timing down is important, but also you can not let the HammerBro get the ball in teh first place. if the goalie has it, get a fast player (dry bones, toad etc) and cover the hammer brother. Try to do what you can to take away that pass option.
dont run in from behind though because thats when your most gullible. run beside him and as soon as he does the deke and touches the ground do a big hit on him. and the good thing is he hardly ever gets an item for it.