The VFL home and away fixture ends next weekend, which means Collingwood's side, which is placed 12th on the ladder, has just two games remaining.
Krakouer and Macaffer have played two games each since February knee reconstructions while Johnson returned last weekend after a May shoulder operation.
Buckley said all three needed to play at least one more game before being considered for the senior team, and he stressed how little football they had played.
"The time will come where we make a call on whether they're right to come up or whether we need to see more of them," Buckley said on Wednesday.
"Time is running out. We've got two more VFL games.
"You've got to remember these guys have played very little footy. Ben Johnson has now played three and a half quarters, Krak's played two games back, Brent Macaffer's played two games back in the VFL."
The Magpies play West Coast at Patersons Stadium in round 22, and its expansive surface might not be the ideal place for a return, especially for the knee pair.
But they return to the MCG to face Essendon in round 23, which could be a better option.
Buckley said it wasn't only those three, who all trained on Wednesday, who would cause headaches at selection committee in future weeks.
"Clearly there's some talent in our stocks that want to take advantage of their opportunities at VFL level and be putting their foot forward by playing great footy," he said.
"They've put the match committee to a challenge, whether it's Johnson, Krakouer or Macaffer, or [Kirk] Ugle, Jackson Paine, etc, [Tom] Young and [Luke] Rounds.
"They're players that want to play good footy and put their name up for selection."
Jennifer Witham is a reporter for AFL Media. Follow her on Twitter @AFL_JenWitham.
