The wing-back's arrival from Benfica marked a return for the former Real Madrid youth teamer.
Speaking ahead of tonight's Champions League clash at Olympiakos, Carreras said: "I'm incredibly happy to be playing my first season here in such an important competition for the club. Olympiacos is a tough team, it will be tough, but I really want to play and win.
"It's super good. We have an incredible group, from the coach to the 25 players. There's a great relationship between us. The veterans make themselves heard when seriousness is needed.
"Every time I arrive at a new club, I'm confident I'll perform at my best. I hope to play a lot of minutes over a long season. I've always believed everything would go well and that will continue to be the case."
On where his best position is, Carreras also shrugged: "I'd play in any position at this club. I'm here to help and do what the team needs. I can play as a centre-back, as a winger, in a back four or a back five... I adapt to everything."