Sorry, but you did not R-E-A-D my post.
First, the kid said he was running Lydiard. He is not. That is my point.
Second, I never said he should run EVERYTHING fast. Just 2-3 times a week should be faster than EASY. IF he is doing Lydiard. It should still be under his anaerobic threshold, and should feel "pleasantly tired" when finished, not like he just ran a race.
Third, I said he should run HIS pace, and NOT force it. He should run what is right for him. However, IF you can not run 7:00 to 7:25 and have it feel relaxed and 3/4 effort a few times a week (as you should IF you are doing Lydiard), then you need to reconsider your goal to what you CAN do.
Finally, Lydiard is not the only method. He could choose LSD based training. Give himself enough time to build a base, and break 3 - assuming he has the talent to do so. A 17:20 5k indicates he might. However, given this training, it is still true that IF he choose to do a faster run one day and can not run a 7:00 to 7:25 pace for 10-13 miles relaxed, then the chances of running 6:50 pace for 26.2 are pretty slim to none.
R-E-A-D-I-N-G. Practice it.