The idea that players who sign late perform bad is grossly exaggerated. Let's look at some examples:
Pastrnak - Signed relatively late, followed it up with a career year.
Lindholm - Signed when season had already started, followed it up with a strong season.
Rakell - Signed when season had already started, followed it up with his best season to date.
Ristolainen - Signed when season had already started, followed it up with a career year.
Gaudreau - Signed when season had already started, followed it up with a weak season.
Anderson - Signed just as season was about to start, had best year to date.
Manson - Signed just as season was about to start, had career year.
Ehlers - Signed just as season was about to start, had a strong season.
These are the first names I found, other than Jagr who I deemed not a good example to use. Out of eight guys, one of them had a weak year. Gaudreau. Now what happened with his game? Well, nothing with his even strength game. Calgary's PP fell apart though, affecting everyone. I sincerely doubt that Gaudreau missing preseason caused the PP to fall apart for a whole season.
In five of the cases, the player followed it up with their best season so far.