Neil Lennon has revealed Celtic have lost 35 players to international duty this week.
The club's Lennoxtown training complex has been like a ghost town as nearly the entire first-team squad and many of the Academy players have departed to represent their countries in matches all over the globe.
The Hoops boss has never witnessed such a mass call-up of players, from youth to first team, for national service.
And although he is happy to encourage his players' international aspirations, he faces a nervous wait until they all return.
"It's right through the club now from Academy level all the way through to the first team," Lennon told the club's website.
"I think we have 35 involved throughout the club which is quite a remarkable stat really."
"I think we have 35 involved throughout the club which is quite a remarkable stat really." - Neil Lennon
He added: "Whilst I would never stop anyone going and representing their country, it can be a very concerning time for me personally, just knowing if the players are going to be okay."
"To compound it all, Scotland are playing Wales (tonight), where I know I have possibly five players playing against one another, and that again is a huge worry for me."
Celtic's season began with the first Champions League qualifier against HJK Helsinki on 1 August, and this international break has allowed the top-team players who remained in Glasgow this week to be given time off to recharge their batteries.
Lennon said: "On Wednesday we only had Kelvin (Wilson) and Gary (Hooper) in out of the first team so we gave them a hard work day and then they will have Thursday, Friday, Saturday and Sunday off, just to go and rest because the amount of pressurised games we have had has been quite intense.
"I want them to just go away for a couple of days, relax and take their mind off football and come back refreshed for going again on Monday.
"It gives them a chance to replenish their body, and it's also important for their own mental approach to have a break."