It’s another week in the NWSL, and another week of some clubs playing without a few of their strongest players as the U.S. continues a series of friendlies against South Korea and Canada plays in Germany.

The league’s reliance on national team players creates a recurring problem that has no easy solution – how can club and country find the perfect balance when it comes to sharing the game’s best players?

This week’s international friendlies fall within FIFA’s reserved breaks, which require clubs release their players for 48 hours for national team duty between June 15-20. But NWSL Executive Director Cheryl Bailey said in planning the season, there wasn’t a way to entirely avoid days when national team players may not be available.

“We did consider the FIFA calendar when we were creating the schedule, but given the length of the season we were not able to avoid playing on two weekends in the league,” Bailey said in an email to NWSL News. “If we had avoided the FIFA dates then it would have created more weekday games, which is not the best for players or the fans.”

The United States played South Korea on Saturday and will face them again at home Thursday, while Canada will visit against Germany on Wednesday.

FCKC's Kristie Mewis and Washington Spirit's Diana Matheson during the USWNT vs CANWNT friendly in June 6, 2013.

FCKC’s Kristie Mewis and Washington Spirit’s Diana Matheson during the USA-Canada friendly in June 6, 2013.

It affects some clubs more than others. Since Shannon Boxx’s injury in late April, the Chicago Red Stars have had no active U.S. national team players on their roster. Meanwhile, FC Kansas City has four in Nicole Barnhart, Lauren Cheney, Kristie Mewis and Becky Sauerbrunn. Most other teams have just two active U.S. national players.

FC Kansas City coach Vlatko Andonovski said the high quality of call-ups presents the biggest setback for The Blues, but added that the preseason served as a practice run while American, Canadian and Mexican national team players were mostly absent.

“We are missing a little consistency and when you’re playing opponents who are only missing one or two players, we’re at a disadvantage,” Andonovski told NWSL News on a call. “But we’re very aware of it and it’s nothing new.”

The Western New York Flash will play at Chicago on Wednesday without Abby Wambach, their leading goal-scorer by a wide margin.

The earliest NWSL game after national teams finish their friendlies is this coming Saturday when Portland Thorns FC visits New Jersey’s Sky Blue FC, two days after the U.S. plays at Red Bull Arena and three days after Canada plays in Paderborn, Germany.

Sky Blue coach Jim Gabarra said the decision to start Americans Christie Rampone and Kelley O’Hara will depend on how many minutes they play against South Korea, but Canadian Sophie Schmidt will be traveling longer to return and may not be ready in time. Schmidt leads the team in goals scored.

“The only strategy you can use with the national team call-ups is try to have the rest of your roster prepared to fill the roles that these players vacate,” Gabarra said in an email to NWSL News. “This period is certainly a disruption to our team rhythm but we knew it was coming.”

U.S. National Team Head Coach Tom Sermanni has had few surprises in call-ups for the South Korean friendlies. The rosters are largely the same, keeping most of the same NWSL players he had called in for the U.S.-Canada “rematch” in Toronto earlier this month and the mini-European tour the USWNT took in April.

U.S. Soccer has been the leading stakeholder in the NWSL partnership formed with the Canadian and Mexican soccer federations. But Sermanni said the existence of the NWSL doesn’t change his strategy for national team friendlies.

“These matches were put into place before the NWSL came to fruition, so we are committed to these games in June,” Sermanni told NWSL News last month. “But even if they weren’t, while I am certainly sympathetic to the needs of the league, I need to look at the call-ups to the national team as I would at any other time and call up the players that deserve to be there.”

Before the June call-ups, Sermanni said he planned to put together the strongest squad, regardless of the gaps it would create for NWSL teams.

“As women’s soccer continues to grow around the world, the women’s international calendar becomes more impacted and we need to take advantage of the FIFA dates,” he said.

A spokesman for U.S. Soccer did not answer questions about the scheduling of the friendlies. The current 2013/2014 FIFA women’s calendar can be viewed here.