Jordan Thompson will be unavailable for Blackpool's trip to Bolton Wanderers on Monday night after being called up to the Northern Ireland squad.
It was initially hoped Thompson would miss just two games following his call-up, next week's home clash against Rotherham United and the EFL Trophy trip to Carlisle United the following Tuesday.
But, despite speaking to Northern Ireland coach Michael O'Neill, Grayson has now revealed the 22-year-old will also miss Monday night's televised game at the University of Bolton Stadium.
Pool will also be without defender Rocky Bushiri, who has been called up to Belgium's Under-21 side.
Sides in League One need at least three call-ups to have a game postponed.
“From my perspective I like to have as many bodies available as possible and have the hard question of leaving one or two players out," Grayson said.
“We’re going to be without Rocky and Jordan who are away on international duty.
“I did speak to Michael to ask if they would let him stay behind for 48 hours. As much as he would have liked to help us out, he just felt it was too close to their game against Holland.
“We asked the question but unfortunately I didn’t get the answer I wanted or would have liked.
“But we’ve got a squad that has got us results over the last few weeks when lads have been injured, so hopefully that will be a case again on Monday.
“It wasn’t a battle with any stretch of the imagination as I know Michael quite well.
“It was a conversation I wanted to have with him because if I had not asked him the question and somebody had said Michael would have been happy for him to play then we would all have been kicking ourselves.
“So I asked the question and he tried to be helpful with us but he’s got to look after himself and it’s his priority.
“It’s a great honour for Jordan to play for his country and we stand by that decision.
“Jordan has only just broke into the team and did really on his first start last month, which pushed him closer to playing for a qualifying game.
“I’m sure Jordan would have stayed behind had he got the green light from Michael but unfortunately that didn’t happen.”
Northern Ireland face the Netherlands in Rotterdam on Thursday, October 10 for their Euro 2020 qualifier, before travelling to Prague the following Monday for a friendly.
Thompson, who has three caps for Northern Ireland, made his first start for his country last month in the friendly victory against Luxembourg.
He produced an impressive performance at Windsor Park, delivering the corner that led to Northern Ireland's goal before going close to scoring in the second half.