The day before a race is the best time to get your legs ready for the following day's race. Just giving the legs a taste is all that is needed. I like to do a 1 hour workout with a 15 warm up and 15 cool down, 2 sprints at 15 seconds, 1 block of 5 minutes at threshold power, and 2x2(3) minute VO2 max efforts. This opens up all the systems and is just enough to leave the legs feeling fresh.
Last year and this year I am training through all the GA cross races to get to nationals. I have found that how you feel on your opening up day is not indicative to how you will do the next day. I have had some pretty terrible feeling opening up days, only to do well in the race.
I do my opening up on Peachtree Road (gasp) between Dresden and Ashford Dunwoody. It is a long straight section and I can do the 2 and 5 minute intervals there no problem. My sprints are done on N. Peachtree just beyond the Gypsum factory.
Today I was able to average 884w and 945w for the 2 sprints and max out at around 1274w. The threshold was a nice 293w average (ftp around 310w) and the VO2 max efforts were around 333w which is low in the zone.
Here is a screen capture of the intervals...