Chelsea won 2-0 thanks to goals from Estevao Willian and Joao Pedro.
Gittens told Chelsea's website afterwards: "Everyone is happy to be back and we have been working hard together on the training pitches. It’s been enjoyable, we have been laughing and joking, but most importantly, we have been working hard. It has been really good so far.
"I feel quite settled already, to be honest. I have talked to everyone, they are all good people here – good souls. Everyone is young, has similar interests off the pitch, and it is easy to talk to everyone.
"I just want to win games for Chelsea and compete for the big titles, that is the main thing.
"Individually, I want to improve as a player, learn from everyone and just try to do the best I can for the team."