I'd like to concur with others that 400-800 guys should not get their endurance from long runs. They can benefit from doing some progressive runs on their longer aerobic day (let's call it Sunday, the distance runner's long run day) during the start of base, but this moves into either 4-5 x a mile with 2 min recovery, or 6-7 x 1km on 90 secs recovery, all at 5-8km pace, and ideally in a park. This continues to be their weekly aerobic session right through the season.
Another aerobic day with some anaerobic can be something like 6-8 x 2 mins with 2 min recovery, basically training at 1500-2km speed. Ask JRinaldi about this session. It's another staple that stays throughout the year.
Another at 800-1km speed with rps of 300-500, and another at 100-200 speed. These are long sprinters remember. They need this.
Add lifting 1-2 times a week, and one or two easy runs which to this type can be a 10-15 min tempo after decent warm-up. Enough to get aerobic benefit, not too much to stop a quality workout the day after.
This is more of an 800 program, but the sprint work, lifting and absence of longer runs would mean a sprinter type 800 runner could still run a good 400.