It’s good to get a fairly deep massage four to five days before a marathon. It will help reduce muscle tightness before your final taper. However, if you’re not accustomed to deep massage, this is not the time to try it for the first time, as it could leave you with too much soreness.
It’s also important that the massage fits in with your training plan. It’s not good to have your deep massage the day before your last interval session, as you could be doing it on deadened legs.
I generally have a deeper massage after my last interval session, when there is no more hard training to do. It’s also useful to have more of a light, gentle, flush-out massage a couple of days before the race.