Marathon off of 5k training....what would you expect?

I'd imagine the best performances would come at the 5k and 10k, maybe the mile too. You'll be able to do the marathon just fine, but without the long specific marathon training runs, the last few miles will be tough and your overall pace will be slower than if you focused on the event. I'd say if you want to pr at everything though, train like a 5k/10k guy. Training for the marathon is going to make you miserable at distances below the half.

I've done pretty much exactly that. It wasn't pretty. It's very hard to hold yourself back enough, because marathon pace feels so much slower than all of the other quality work. I was hurting pretty bad at 16 miles, and by 20 it was a joke. I was running like 7:45s.

The real problem is that my long runs were just 14-18 miles, and at a pretty easy pace. If I pushed the pace on my long runs, I'd never have been recovered for the kinds of track workouts I was doing.

Now, if you have enough time after your track season, and you're not totally fried from too much intensity, then you should be able to do a 6 week race specific cycle and pull off a decent marathon. You should be aerobically very strong. The main thing is getting in lots of long miles at MP. Also, a small cut in mileage will facilitate more recovery so that you can jam a little more quality into such a short time frame.

What if you just hammered your long runs? Do you think that would strike a balance between satisfying marathon performance requirements and allowing you to recover for track workouts?

As a seventeen year old, I ran a marathon on a bet. Was a high school two miler-nothing special-10:20 or so. Had not run more than 12 miles ever-and averaged about 60 mpw for the previous year. I ran a 3:27. Jack Daniel's VDOT tables would say I should have run 2:53 ish. No long runs hurt me. Needless to say, I didn't negative split.