When Kamworor went by Cheptegei, he was already really slowing, and within seconds totally rigged. When the broadcast showed him in the final stretch, with runners streaming by, my girlfriend said "wow, I could run that fast." (And she's not really a runner.) I wasn't sure. He did look horrible, but for a guy at the level even horrible might be faster than it looks.
So I wondered, how fast/slow was he moving at the end?
First of all, the final lap splits: Kamworor 5:51, Cheptegei 7:47. With 2km laps, that is 4:42.4/mile pace for Kamworor and 6:15.7/mile for Cheptegei, for the whole lap. (Interestingly, Kamworor actually slowed on the last lap, too; his overall pace for the whole race was 5:40.8 per lap or 4:34.2/mile.)
But what about the final stretch, after Kamworor went by?
The LetsRun write-up on the race says that Cheptegei finished "some 1:40 behind Kamworor (who only took the lead with 2:10 left in the race)."
According to the results, Cheptegei finished 1:44 behind Kamworor, and the added fact from LetsRun that Kamworor passed 2:10 before finishing is useful because we can find a ratio of their paces from the time post-passing:
Seconds to finish (post-passing)
Cheptegei/Kamo ratio (post-passing) 1.80
And using this ratio we can figure out Cheptegei's pace post-passing, relative to Kamwo's final lap pace:
Kamwo final lap pace (seconds/mile) 282.4
Kamwo final lap pace * ratio = Cheptegei pace (post-passing) 508.3
That is 6:28 pace. Granted, that is still an average over that period as he slowed down from ~4:4x mile pace to absolutely blown up over the course of a few hundred meters. But it is pretty impressive that even absolutely locking up to a near-walk, Cheptegei still covered ~740m faster than my GF's 5k pace. (I won't say how long I could run 6:28 pace, but let's say this was humbling for me, too.)
(Limitations: This makes the assumption that Kamworor ran the last stretch at the same pace as his last lap overall. If he was covered that part a few seconds faster/slower than the pace I am using, then Cheptegei's final stretch pace would also be a few seconds faster/slower than my estimate.)
Overall, Cheptegei's hanging on was admirable already, but the fact his team got bronze by three points is extra cool. If he had been five seconds slower, we would have been passed by three more guys and lost the team medal!