Renato, I do know the talent of Marcel Jacobs. Because I can research it and I have a completely objective take on it (not an emotional/inherently biased take a countryman of his would have, for example).
3 seasons and 45 races resulted in seasons bests that oddly pointed a level of sprinting in the 10.1 second performance range. This is not a limited or small sample set. This is considerable. A single season jump to 9.80 which took him from the position of 420th fastest man ever to 10th is inconceivable - and especially if you want to contend a main factor is a "mental coach". No other top 10 sprinter in history ever progressed even as close to this - except for our good friend Ferdinand Omanyala from Kenya who btw has already served a doping ban.
Since you are distance coach let's put this into perspective and I'll give him the benefit of using his 10.03 (+1.7) as the benchmark vs 10.11 which is his wind adjusted level.
That's the same as 1500m runner stuck at 3.33 (3.33.49 to be exact) coming out and dropping his PR to 3.27.84. Or a 1.44.27 800m runner dropping to 1.41.72 in a season.
But as a true athletics mind with high intelligence you would immediately know how implausible and ridiculous that is - you might even say something to the effect of "ma che dici"
So spare me with your "got a new coach" sciocchezz my friend, I don't care how good of a coach you are.