The 26-year-old has not featured for the team since December last year, and has managed two goals in just three league appearances so far this season.
Riveiro insisted it is not part of his operation to respond to questions on the non-availability of players in the team.
"Well played, but I don't do it. I don't speak about health of my players, it's something that belongs to a private space," said Riveiro.
"And the moments the club feels it's time to speak about which players are injured and how long they are going to take, which moment of the process they're in – they'll do it.
"It's not part of my job description because, like I said, it's not an ethical thing. I know it will be nice to know how close Olisa [Ndah] or [Goodman] Mosele, and what's happening with Saleng. But it's not going to happen."
The Ghost have not been happy about Saleng’s absence since the turn of the year, having been instrumental in the club’s successes over the past two seasons – including winning the Player’s Player of the Season award in 2022/23.
Saleng has scored five goals and provided an assist in the 13 appearances he has made in all competitions this season.