Mertens wants to see the club keep buying.
“I came here six years ago and a lot of transfers have gone through, a lot of good players come every year. It's very important for a club like Napoli to know where we're coming from and where we're going," said Mertens.
“The problem is we are that close to making another step and it's important to make that final step. I don't know how we're going to do it, but we have to keep on buying players.
“It's difficult, because in the end if you buy the best players, you have the best team. I think the way we're doing it now, some players together for six or seven years, that is important also. At the end of the day, to win trophies, you need some more steps."