The simple method:
Backline players- Play in the back half with short bursts of sprinting when preventing the forward from getting the ball and general jogging and walking around the play. Would be about half and half of anaerobic and aerobic due to high rest periods.
Centre/Midfield players- Play everywhere and follow the ball as their job. Sprints are often but short distance although lots of jogging means that they are anaerobic for a short while but primarily aerobic after about 5 minutes pending on whether they go to the interchange or not.
Forwardline players- Similar to the backline players but roles reversed. Although a forward player may play on the wing which requires longer harder sprints.
Ruckman- More or less jog with small sprint efforts here and there. Use explosive actions to get up and jump to tap the ball to the midfield.
Fitness components:
Backline: Cardiovascular endurance, anaerobic power, LME.
Centre: Muscular power, cardiovascular endurance, anaerobic power, LME.
Forward: Same as backline.
Ruck: Muscular power, LME, anaerobic power.