This will be easy. Japan closes out its home soil World Athletics Championships with one last race, and one of its traditionally strong ones, the men's 4x100 m relay.
21:20 - Men's 4x100 m Relay Final
Prognosis: This is the entry pool:
Abdul Hakim Sani Brown (Toray) - 9.96 (+0.5) - 4th, Heat 7, Nationals
Yoshihide Kiryu (Nihon Seimei) - 9.99 (+1.5) - 1st, Nationals
Yuhi Mori (Daito Bunka Univ.) - 10.00 (+1.3) - 7th, Nationals
Hiroki Yanagita (Toyo Univ.) - 10.00 (+0.3) - DQ, Nationals
Sorato Shimizu (Seiryo H.S.) - 10.00 (+1.7) - 4th, SF3, Nationals
Yuki Koike (Sumitomo Denko) - 10.08 (+0.3) - 5th, Nationals
Naoki Inoue (Waseda Univ.) - 10.12 (+0.4) - 4th, Nationals
Naoki Okami (Aomori Pref. Gov't) 10.17 (+0.9) - 2nd, Nationals
Towa Uzawa (JAL) - 20.11 (+0.9) - 1st, Nationals
In the individual 100 m Sani Brown confirmed that he wasn't anywhere close to peak form, and he was left off the 4x100 m team in the relay heats. The lineup there, Koike, Yanagita, Kiryu and Uzawa, ran a 38.07 for 3rd in their heat to make the final, lucking out a bit in South Africa and Great Britain both self-eliminating from the same heat, and a little more with Jamaica not making it out of the other heat. Koike was arguably the weak link on the team on paper, but he still ran well enough to get the job done. The question is what lineup changes might happen to try to get the extra bit they'll need to move up 2 places in the final.


Comments
That said, I'm not sure what they could do. If I'm allowed, I'll give some exemples with the splits.
I don't know how reliable the single splits are but it seems like Kiryu was one of the worst of the 3rd section and Yanagita was ok but a bit too slower than the medal contenders. Uzawa had the best 4th section (ok Lyles and Thompson weren't there but that's not the point), Koike had an average first section.
Compared to their SB at the world relay, the big difference is that Uzawa ran the third section there, 9,19 vs 9.50 ran today by Kyriu. Sani Brown ran a much slower than Koike (10.54 vs 10.38)while Atago and Inoue ran pretty much the same that today Yanagita and Uzawa today.
That said, I have no idea what they practiced and if they are open to change (I doubt it) but what I'd notice is: Uzawa ran 9.19 at the Worlds and that was an elite time. You don't swap someone running the third section with that split out, it's a difference maker towards the field (beside US and Jamaica).
I'd say you could make a case to put Uzawa in 3rd, keep Koike or push Kiryu in first, keep Yanagita in second and put Inoue back in the 4th.
The outsider could be Shimizu since he runs both 100&200, they could try and make a 3rd&4th section with him and Uzawa, whatever order they like (If I have someone running the 3rd section as good as Uzawa I'm leaving it there).
I doubt there will be changes, they likely will go with a more risky approach at the exchange points and take it from there but i think anaylising data the changes I suggested could make sense, if they ever prepared for a similar scenario. Though from what I read pre world championship is they were dead set on Kiryu 3rd and Uzawa 4th. If they want to go down that route again they need a perfect start from Koike something more from Yanagita (don't think he has that vs elite runners), at least 0.15 better from Kiryu and better last 20 meters from Uzawa with perfect exchanges.
It's a lot to ask but the relay is unpredictable, I hope they pull something great off as my national team (Italy)is out.