Must-do exercises: plain-old squats and deadlifts.
"Playing soccer greatly increases your risk for ankle sprains, hamstring pulls, and ACL tears," says Jason Ferruggia, a performance-enhancement coach in Warren, NJ. These classic lifts fortify the musculature of the entire lower body, and stronger legs will prevent injury and allow for increased speed and power on the field. If you really want to perform at peak level, invest in a sled (you can pick one up at elitefts.com). Running sprints with it attached to your waist will build tremendous speed—the kind you need to be the first guy to reach the ball.
The right kind of cardio: "Soccer involves bouts of short sprints followed by jogging and sometimes even walking," says Ferruggia. "So interval cardio is ideal." Try sprinting for 5–10 seconds and then backing off to a 30-second jog followed by 30–60 seconds of walking. Repeat this sequence for 20–30 minutes. "This will give you the feel of being in a game," says Ferruggia, "while preparing your heart and lungs for the season."
Train flexibility: "A lot of soccer players suffer from shin splints," says Ferruggia. You can prevent the injury by stretching your calves. (Do this in the midst of a calf-raise workout, holding the bottom position of a rep for five seconds.) You should also build the strength of the calves' antagonistic muscle, the tibialis anterior (the muscle on the front of your shin). Simply place a dumbbell between your feet and raise your ankles up and down. That's one rep. Perform 2–3 sets of 10–20 reps, resting 60 seconds between sets.