This is just a short overwiev of van Niekerk’s only two 400m races of the season before the 2017 IAAF World Championships in London.
As always, note that these splits aren’t official and should — at best — be rounded to tenths instead of one-hundredths of a second. I used my own methods to estimate the splits using 50 fps videos of every race, but it’s impossible to get conclusive and 100% correct splits.
SPLITS

Based on his recent run of 30.81 in the 300m in Ostrava, I’d say that he has much more to give in his middle part of the race.
Last year his personal best in the 300m was 31.03 and he pretty much replicated this time on his way to a new world record in the 400m. In both of his 400m races this year, however, he has been about a second slower than his 300m PB at the 300m mark.
We will have to wait and see if this is just due to him
a) experimenting with different race strategies in what are essentially prep-races for the biggest race of the season,
b) having a hidden extra gear in the middle part (100-300 m) or second half of the race. His fastest middle part of the race this year has been 20.8 in Lausanne. In Rio it was 20.3.
c) losing some speed endurance or endurance in general because of his newly developed speed taking its toll and making him uncomfortable to run the first three quarters of the race at virtually full speed.
STRIDES

All I will say here is that his stride length is still phenomenal and has, in fact, even lengthened overall.
2017 Season So Far …
2017 Season's Best Times (pre-London World Championships)
100m: 9.94 (+0.9) Velenje, 20 June -- Personal Best
200m: 19.84 (+1.2) Kingston, 10 June -- Personal Best
300m: 30.81 Ostrava, 28 June -- Personal Best (World Record)
400m: 43.62 Lausanne, 6 July
I think he just needs to brush up his race strategy and he will be in prime position to challenge for a new world record.
Žiga P. Škraba