In a bid to reduce their wage bill, Liverpool loaned out the Spanish goalkeeper, who reunited with former manager Rafael Benitez in Naples.
Reina has made a strong start at high-flying Napoli and became the first player to save a penalty from Mario Balotelli in a game in his side's 2-1 win over Milan on September 22.
The 31-year-old said his loan move came as a surprise and believes he may have played his last game for the English Premier League club.
"At the moment it's difficult to think about being a Liverpool player next year. They have a young goalkeeper in Simon Mignolet and the manager prefers him to me," Reina told the Daily Mail.
"That's the reason why I'm here and he will be at the club next year as well. There's no reason to think I'll be a Liverpool player from now on but we'll see where the future takes us.
"It's been a good move so far and I don't regret what happened. I would have preferred to say goodbye in a different way."
Reina, who had been linked with a move to Barcelona, said it was a shock when he received the call telling him he was set to be loaned out.
"It did come as a surprise," he said.
"It was the club who made the move. I was on my holidays and nobody told me anything.
"Suddenly Napoli called and said they were agreeing terms with Liverpool and Liverpool just rang me two days later and said the same. They probably had their own reasons."
Reina has three years remaining on his contract at Liverpool but said his focus was firmly on performing well this season and earning a spot in Spain's squad for the 2014 World Cup.
"I want to enjoy this year. It is such an important one for me with the World Cup around the corner and returning to the top flight, playing in the Champions League and fighting for the title, is something I have missed in the last two or three years," Reina said.
"I'm happy to be back at this level. I never expected it but it's been a great decision. I feel invigorated by the move.
"Mentally, I'm fresher, I have more hunger. It is not like before I wasn't, but a change can be good for your mind.
"You have to show the people even more and you have to be ready. The tactics and the managerial skills of Rafa are getting the best from me and that's one more reason."
