One of my training partners is a lifetime football player, a former defensive back through college, also ran the anchor leg of the 4x400 through HS. His sprint speed is off the charts. No lie it's jaw-dropping to see him outkick runners at the track from 50m-100m.
Move the distance beyond 400m, however, and he immediately starts to struggle. I've spent the past year+ working with him, and in that time he's run his first two 5Ks, each time getting faster. He's also run a half marathon and he ran a mountain relay where he racked up 18 miles over 3 legs. Nothing to write home about, but big for a guy who never did distance. He's logged a couple of 16 milers with me.
Long story short, how can I tailor group workouts to help him prepare for a marathon (faster/shorter reps with more rest gradually moving to longer/slower)? The stuff I'm giving my other runners doesn't seem to be working as well for him although all of the runners (this guy included) are coming from the same level of base fitness.