Leader Marseille, which has won all three games, can restore its four-point lead over PSG if it beats visiting Monaco on Sunday night.
PSG needed a handling error from visiting goalkeeper Mamadou Samassa to break the deadlock in the first minute of injury time, when Rabiot kneed the ball over the line after Samassa palmed a shot into his path.
"It's my first goal for PSG," Rabiot said. "I'm happy the coach gave me my chance."
Two minutes later, Ibrahimovic ran onto a long pass, muscled defender Jeremy Sorbon off the ball and slotted it past Samassa for his first goal in five games this season.
The win moved PSG provisionally up to second place with eight points.
Earlier, seventh-placed Lyon's losing streak increased to four matches after being defeated 2-1 at Evian.
Striker Edinson Cavani and center half Thiago Silva both hit the crossbar with headers from corners in the first half. Ibrahimovic had almost scored in the fourth minute with a curling free kick that hit the post, and winger Ezequiel Lavezzi missed an open goal as the rebound landed at his feet.
Despite fielding three players each costing more than 40 million euros ($52.5 million), PSG failed to show any attacking flair for most of a drab first half.
Rabiot pounced when Samassa tried to pat the ball down after saving a header from a corner, rather than just pushing it wide, and it slipped out of his grasp.
"You have to try and give (homegrown players) some playing time," Blanc said. "If they respond well, I won't hesitate to pick them."
The fact PSG threaten most from corners is indicative that its buildup play remains fairly redundant and one-paced.
Guingamp has nothing like the sort of money being pumped into PSG by Qatari investors but was mostly untroubled until the 36th when Samassa was called into action.
He tipped over Cavani's glancing header from a corner, then saw Silva's header come back off the crossbar from the ensuing corner, and moments later made a smart double save to deny Cavani and midfielder Thiago Motta.
Cavani cost 64 million ($84 million) in the fifth most expensive transfer in history and looked the most threatening player. His angled shot was scrambled off the line shortly after the break and then he volleyed wide from a tight angle in the 65th.
PSG enjoyed a big reprieve in the 76th when Mustapha Yatabare went clean through on goal, only for his shot to hit goalie Salvatore Sirigu's face.
Meanwhile, Lyon's day got worse when midfielder Yoann Gourcuff limped off at halftime clutching the back of his left thigh.
Coach Remi Garde was angry with the attitude shown by his players, with five members of the starting lineup homegrown.
"Of course I'm worried, especially if we carry on like this," Garde said.
Striker Kevin Berigaud put Evian 2-0 up at halftime before midfielder Jordan Ferri replied with his first goal in professional football.
Lyon has one of the most highly reputed academies in European football and there were six more homegrown players on the bench.
In Saturday's other matches, it was: Bastia 2, Toulouse 1; Lorient 1, Valenciennes 0; Reims 0, Nantes 0; Rennes 0, Lille 0, and Sochaux 0, Ajaccio 0.
Striker Vincent Aboubakar scored Lorient's goal, while Romania striker Claudiu Keseru and midfielder Christian Romaric scored for Bastia.
Saint-Etienne hosts Bordeaux and Nice faces Montpellier in Sunday's other games.
