With a 27:48 in his DEBUT road 10k, Lagat has now shown CURRENT ability in the low-27s. Easily. Since that course was far from pancake-flat, I'd give him even more than the 30-second rule of thumb, putting him almost SUB-27 if he ran a perfect-everything (weather, pacing) 10,000 next week. In short, he could have the AR this year or next. (If he even wants it, that is. Lagat is a RACER not a time-trialist.)
On that note, given Lagat's uncanny ability to WIN RACES even against runners with faster PRs/time-trial ability (e.g. in the 3000 and 5000), it is OBVIOUS that he is going to totally annihilate Rupp and every other US runner in the 5,000 and 10,000. Noting that Rupp has an uncanny ability to LOSE races and has never won a major international race in his career, it seems obvious that if both of them are on the line in Rio, Lagat places ahead of Rupp.
Rupp should escape to the marathon, like yesterday. Why bother with yet another two mid-pack finishes in the Rio 5000/10,000 finals?