Over play players and niggling injuries become more serious and the public want to see the best players at their best "so while they want to see the top players playing every game the reality is it can't happen".
Hadlee, the former world test wicket recordholder with 431 from his 86 tests, is impressed with what he's seen from some of the newer players.
"I like the look of Corey Anderson. We know he can power the ball over the boundary but I've been impressed with his bowling at the death, his change ups.
"He moves it around a bit and bowls over and round the wicket, so he has nice variations.
"Jimmy Neesham, particularly for Otago in the Champions League, was really impressive, so with more cricket for these guys at international level I think they'll grow and get more confident."
And as Hadlee pointed out, if New Zealand hadn't looked beyond a hardcore group of players to appear in all three forms, possibly the Andersons, Neeshams and Colin Munros would not have been sighted in the national team. All have made an impact at various stages in the past few months with bat and ball.
Anderson won't be in New Zealand's team for the deciding ODI tonight, having headed home with a rib injury.
An MRI scan has ruled out major damage but his sights have now turned to the West Indies visit. New Zealand, having won a thriller in Hambantota on Tuesday to take an unbeatable position with one game remaining, are eyeing a rare overseas series win.
Chasing down 198 in 23 overs to win the rain-affected second ODI - after the first was washed out - was a good example of how batsmen have changed their vision in terms of what is gettable batting second in limited-overs cricket.
"It goes to show with the introduction of T20 in recent years, it's given batters confidence to chase any total down," captain Kyle Mills said.