I have done the following workouts.
10 by 800 done in 2:35-8 with 30 seconds walking rest
20 by 400 done in 73-76 seconds 30 seconds walking rest
6 mile tempo done at 5:45 started descending
3 by 15 min split tempo holding 5:30s
1 year of really tough running with 3k miles on my legs. No recent run race results.
Probably based on the first workout. Fortunately, unlike other posters, his workouts have short rests so you can actually predict something. I'd say sub 16 for sure.