Soccer entails a combination of jogs, sprints, stops and pivots. When cleats aren't correctly sized or properly broken in, painful blisters can result, especially on the backs of heels and the soles of the feet. The best way to avoid blisters is to prevent the common causes of them.
Wear properly fitted shoes that aren't too tight or too loose. Excessive foot movement can cause rubbing that results in blisters, while shoes that fit too tightly can cause blisters from excessive pressure. If you identify "hot spots" on your feet, those areas that become sensitive and red while wearing your cleats, place a barrier such as moleskin over the hotspot. You can also lubricate the hotspot with petroleum jelly to minimize friction.
Between games, wear flip-flops or sandals to encourage your feet to stay dry, as constant foot moisture can lead to blisters. When you're in your cleats, wear thin, sweat-wicking socks and foot powder to help keep your feet as dry as possible.