Former Gunners captain Fabregas completed his protracted return to boyhood club Barcelona on Monday in a £35million deal.
Fabregas pinpointed Wales captain Ramsey as the player who he thinks can successfully fill the midfield void created by the his departure, and Sagna agrees that youngster is ready to make the step up.
Despite being only 20, Ramsey took well to the task of dictating play in midfield during Tuesday night's 1-0 win and set up Theo Walcott for the Gunners' match winner with a perfect cross in the fourth minute.
That, Sagna claims, shows Arsenal will have little to worry about in midfield this season despite Fabregas' departure.
"Cesc is a great player. He was one of our best players but that's part of football," Sagna said.
"Every season we start a season and some players leave at the end of it. That's what happens and I just want to wish him good luck. I will miss him of course but Aaron Ramsey did very well and he will show he is a great player as well."
The match was overshadowed by another potential conflict between Arsene Wenger and UEFA, with the Gunners boss apparently breaking rules by communicating with his bench from the stands while under a touchline ban.
The Frenchman could be fined but should be okay to return to the touchline for what promises to be a tense second leg in Udine.
Before that match in Italy, the Gunners face Liverpool at the Emirates Stadium on Sunday.
Samir Nasri, who has refused to sign a new contract amid interest from Manchester City, missed last week's draw at Newcastle through an apparent illness and may be left out again this weekend if he has not completed his move to the Etihad Stadium by then.
Sagna hopes his compatriot will be available to play against the Reds.
"Everyone knows his about his (Nasri's) quality. I hope he will be back for Liverpool," he said.