Hello,
You can use the Cooper Test to monitor progress throughout the season. The test gained more popularity because everybody is tired of the Beep Test (which I like more).
Look for more references on this website:
http://www.brianmac.demon.co.uk/gentest.htm
What I used in the past:
<1600 very poor
<2000 not good enough
min 2200 for Front Five
min 2800 for Backs, Half Backs
min 3000 for Back Row
I worry more about the <2000 scoring players - below this fitness level everything collapses: motivation - technique - concentration - .... This groups gets my special attention.
Hope this helps,