The Spain international has spent the 2013-14 campaign with the Serie A side after his parent club signed Belgian stopper Simon Mignolet from Sunderland in the close-season.
Reina recently declared that his future is uncertain amid rumours of a possible return to Spanish champions Barcelona, with whom he started his career, although he remains under contract at Anfield.
Rodgers, however, is convinced that the former Villarreal man will not ply his trade on Merseyside next season.
"He wrote a goodbye letter didn't he?" Rodgers said.
"Obviously Pepe made it very clear when he went to Napoli that he was looking to move because he penned a great big letter saying he was going to work with the best manager that he'd worked with (Rafael Benitez) and thanked him for his time for Liverpool.
"So, for me, it probably sounded like he'd made his decision there."
Meanwhile, Rodgers has urged his entire team to take more defensive responsibility after witnessing them concede three goals in the dramatic 4-3 win over Swansea City last weekend.
Liverpool have scored more goals than any other side in the top flight this season with 70, but have also shipped 35 at the other end.
Newcastle United are the only team in the top half of the Premier League to have conceded more, and Rodgers is eager for his title challengers to be more secure at the back when they visit Southampton on Saturday.
"Defending is about everyone, it's not just the back four and the goalkeeper," the Northern Irishman told the Liverpool Echo.
"We didn't defend well enough as a team last week. We didn't press the ball well enough at the top of the field.
"We didn't keep the ball well enough, we didn't make enough passes. It was more a collective issue than any individual. We need to defend better as a team.
"This is a team which is evolving and improving all the time. It was a huge task when I came here to improve our goal scoring and that's something we've done. As this team grows we will improve in other aspects."
