How quickly do you lose conditioninig

John Banks said:

I injured myself during my current training program for a marathon
next Sunday (05/28).

Yeah, you shouldn't have been doing this:

http://www.metacafe.com/watch/1260/amazing_breakdance/
http://www.metacafe.com/watch/129566/elsewhere/

I get injured when I do that too.

Quoted message said:

I was thinking of doing either some repeats or a tempo run on Thursday,
then rest Friday, 2-3 slow miles on Saturday - any suggestions?
Have I missed too much training to still achieve this goal?

You won't have lost a lot of conditioning in three weeks. Stop
listening to that devil on your shoulder, whose voice gets 30 dB louder
during the last week of taper!

Even supposing you had lost conditioning, it's too late to get it back.
Training adaptations take longer than 48 or 72 hours. The miles and
workouts that really count for your marathon were already in your legs
weeks ago.

So physiologically, about all you can do at this point is tire yourself
out or exacerbate your injury. Psychologically, well I'm probably not
the one to be giving advice, but if that brisk six yesterday didn't
convince you the legs still work well, it's hard to guess what might.

My recent personal experience is of four weeks reduced (about 25% lower
miles than the preceding weeks, and almost no hard workouts) training
due to illness and travel. After two of those weeks I had a
breakthrough 10M race, far far better than any in my past, and after
four I enjoyed similar results at a 10k. Again: the training that
matter most in this week's race took place a while back.

John Banks said:

I injured myself during my current training program for a marathon next
Sunday (05/28). My last quality workouts were during the week of
05/01/06 - did a great 10x800 workout early in the week, then my last
big run of 20 miles that Saturday (05/06).

May have pushed too hard that week as I have had nagging injuries,
namely ITBS, since then. So, the majority of my runs since then have
been 4-6 miles at a slow pace.

Was able to rest a bit and decided to try to get in a few quality
workouts this week before the race - did 6 miles on Tuesday at 6:26
pace, took today off. I am getting a cortisone injection tomorrow just
in case.

I believe I had conditioned myself properly to hit a 2:55-56 time in
the marathon - or at least I was in that condition in early May.

How much of that have I lost over these past few weeks?
How should I approach these last few days? I was thinking of doing
either some repeats or a tempo run on Thursday, then rest Friday, 2-3
slow miles on Saturday - any suggestions?
Have I missed too much training to still achieve this goal?

Any input/suggestions/comments welcomed

A few yrs. ago I sprained my ankle on a training run 2 exactly weeks
before a marathon. It was a very mild sprain, maybe more like a strain,
but to be safe I didn't run at all for the remaining 2 weeks. I did
fine in the race, lost nothing as a result of the lay-off.