Muscles recuperate best if given 48 hours to rest. This doesn't mean that you should not run more than two days in succession, but you should think seriously before running hard two days in succession. Regardless, Monday is always a day of cross-training for those in the Intermediate program, before or after the marathon. This is an increase of one mile from last week's Tuesday workout. I'm trying to get you back to a steady-state level, and one way to do it is to institute slight mileage increases.
Sudden increases offer a route to injury.
Run 3 x mile, jogging 3-5 minutes between. Run your miles at about the pace you would run that distance during a 10-K race. This is a pace increase from the marathon pace I asked you to run these miles in last week. Slightly tougher, but still not that difficult a workout considering you are in your post-marathon recovery mode. You might be more comfortable running this workout on the roads rather than at a track.