It sounds like less of a problem with your defense and more of one with your offense...probably the middies.
You need to maximize your possesions. Instead of getting the ball, running down the field and shooting it right away, bring the ball downfield and SLOW IT DOWN. Run a set offense and take your time. By default, your defense will get the chance to take a breather and calm down, and you'll spend more time on offense.
In practice, start off with a fast break. If there's no good shot to be had, pull the ball out and slow it down. Move it around the offense at least twice before anyone dodges or takes a shot. Take your time with the ball and DON'T FORCE ANYTHING. Keep moving the ball until their defense breaks down, and then try to score.