Nigel Worthington has urged his Northern Ireland players to secure regular first-team football.
Northern Ireland have mounted a strong challenge for World Cup qualification but will miss out on a play-off place if Slovenia secure at least a point against San Marino on Wednesday.
Worthington's men bring their Group 3 campaign to a close with an away game against Czech Republic but the manager is already looking forward to how the team can improve in future.
He is worried that many of his men are not getting enough games at club level and has called on them to play more regularly - even if it means moving.
"To go and play our way at a high tempo with good quality, some of our players can't do that in two games in four days," said Worthington.
"That's been most evident on the couple of occasions where we've had double-headers. In the first game the performance level would be very good, the energy levels were first class - and the next game, energy levels had dropped.
"I can do nothing about that, because players are tied to clubs and they come to the international set-up.
"My message to the players is that if you're not in your club teams, work hard to get in it or get yourself out.
"It doesn't only affect them as the individual; it affects us as an international team, and that's something that's been ongoing in the campaign.
"You can live with three or four floating around outside the first teams at their clubs. But you can't have 15 or 16 - that's a huge amount, it really is."
Worthington announced on Tuesday that senior trio Aaron Hughes, Maik Taylor and Stephen Craigan had all committed to playing on at international level.
Skipper Hughes is set to win his 70th cap in Prague and Worthington believes he is an excellent role model for younger members of the squad.
"One word sums Aaron up, and that is professional," he said.
"He is a fantastic leader, sets the right examples and goes about his business in a very controlled and quiet manner."