Hager is confident most of them will be back. So the younger players, who have caught his eye, will need to take their chance against India and in Brussels.
"In Hawke's Bay (where they successfully defended their title against Australia, the United States and Japan last month) they showed they're capable, and that's quite pleasing," Hager said. "I have a bit of a saying: be wary when you lend your hockey stick; you may not get it back."
There are conditions for the six absentees if they want to get back into the Black Sticks. They must play the National Hockey League tournament, which is in Wellington in mid-September. The Commonwealth Games on the Gold Coast in April is a high priority.
"I will have discussions with those players about training programmes because, from my point of view, those players have to be training and playing late this year and not just expect to return in January and be ready to play," Hager said.
The women's Black Sticks will play at least 40 internationals this year. Burnout becomes an important factor.
"We have to manage it better in future," Hager said.
There are plans to develop a national club competition to enhance the pool of talent. That could trim the amount of overseas trips they make each year. But, even then, there's a problem.
Many of those trips are for qualifying events to advance to the next stage of the big international tournaments, such as World Cups and World Leagues.