The Gunners first choice right-back has missed the past four months after breaking his ankle against Tottenham Hotspur in October.
Sagna completed his comeback when Arsene Wenger sent him on as a late substitute in the FA Cup win over Aston Villa at Emirates Stadium on Sunday, and he has admitted it was tough to spend so long out of action.
“I am absolutely delighted. It's been quite difficult all these months - four is a long time,” he told the official Arsenal website.
“I just needed to get back as quick as possible and now I finally am. Now I just need to work even harder to get back because I have only had two training sessions and it is not easy. But I will do it.”
The France international’s introduction to the fourth round tie was greeted by huge cheers from the Arsenal supporters.
Wenger will have been relieved to have him back in action as he has had to do without all his natural full-backs for some time.
The Gunners boss has not been able to name a specialist full-back in a match day squad since December 6 and the Champions League tie with Olympiakos, where Brazilian left-back Andre Santos suffered ankle ligament damage.
However, Sagna does not expect to walk straight back into the first team and insists he will need a number of games to return to something like his best.
“I will still work with the fitness coach but I will only get fit by playing games,” he added.
“I am just biding my time to start a game now but I am not rushing. I just want to give the maximum to get myself into the best position.
“It was nice to have support from my wife, kids and my friends. The fans have also supported me a lot during my recovery and it was quite helpful when I was working.”