The World Cup is the biggest event in football by far, despite what people have remodified it to to suit the performances of Messi/Ronaldo in it. Most players, even for strong nations, get one or two chances to play in it over an entire career, and fewer still will experience going deep in the competition.
I still believe it's the one tournament that players risk everything to participate in: lying about injuries; playing the biggest games on permissible numbing agents if crocked (which can have longstanding ruinous effects on the remainder of their career) and so on and so forth. There are players who will put country before club, despite the latter paying their wage and being their bread and butter.
There's no way some players aren't saving themselves for the tournament, I would say. If you're a guaranteed starter, and are therefore not having to use the remaining time and games to convince a manager to take you, you'd be a saint and consummate professional to give your all in some relatively insignificant 3-pointer over self-preservation for the biggest event and spectacle that rolls round every four years.
As the window between being moderately injured and it costing players their spot narrows, I should think there'll be a good amount of assured starters playing within themselves.
At the other end of the spectrum, and what balances things out, is there are players in last chance saloon to impress and make the trip, and it would stand to reason that they are pushing themselves harder and risking more as well as masking injuries that they'd otherwise not in their last gasp attempt to be taken.
He has never played an international tournament though and we really love our national team here, unlike England.