Train with your club/team on Tuesday and Thursday. Play on Saturday/Sunday. That is the normal template for most teams. If that is the case for your team, then maintaining your conditioning levels is fairly simple to slot in to this regime.
Tuesday nights are historically when most teams do their toughest session of the week. This session may contain a fair bit of contact and some running. Some teams will scrummage, do lineouts and even work on mauling. If that’s the case for your club, then all your fitness needs are contained within the session which is great. I don’t feel there is any need to do any fitness work on top of this type of session as all the fitness aspects of rugby are covered.
The following night (Wednesday) should be used as rest and recovery before returning to Thursday nights session. This session usually amounts to a more technically based session. I would feel that at the end of this training unit you could do a 10-15 minute anaerobic segment, which would top up fitness levels. Although it may appear there is not a lot of time dedicated to fitness in the training week, I would view the whole week holistically and break down the week as follows into training units:
Saturday/Sunday Match (as good as 2-3 units of training)
Monday Rest or Recovery or weight session
Tuesday Hard club training session (as good as 2 training units if high intensity)
Wednesday Recovery or light weights session
Thursday Technical training session (followed by 1 10-15 minute unit)