Luisinho says Deportivo La Coruna must block Juanfran from joining Barcelona.
Barca want Juanfran as an emergency signing to cover injured fullback Aleix Vidal.
Luisinho says: "[Juanfran] should not be able to leave, it would be a significant loss.
"He shouldn't be allowed to leave because the transfer window closed. He doesn't know anything concrete, either, and is happy here. He already rejected other offers.
"Juanfran is a really impotant player for us, he's having a good season. If he has to leave, then hopefully it's for his own good, but we know it would be a big loss because he's a vital player for the team."
Source: tribalfootball.com