Correa has not played for over a month due to a hamstring injury, while Skriniar has been sidelined for the last two weeks with a back injury.
"Correa has returned (for training with) the group but won't be available for Spezia. Unfortunately, Skriniar is still out, but I'm hopeful he can join us for training on Saturday," Inzaghi said.
"We're learning to cope without Skriniar as best we can."
Inter will play against a 17th-placed Spezia, who are hovering three points above the relegation zone. Inter are second, 15 points behind leaders Napoli.
"I'm expecting a tough game against a team who are fighting for a clear objective (to avoid relegation) and who have recently changed head coach," Inzaghi said.
"They're on the back of two good draws so we'll have to play the game as best we can, making sure we do the basics right."