Juan Mata admits he is unsure if David de Gea will be at Old Trafford next season

Keep your friends close and your secrets closer.

With every passing day, speculation mounts about a seemingly imminent Real Madrid bid for Manchester United goalkeeper David de Gea. The Spaniard has been closely linked to Real all season and has only a year remaining on his United contract. Louis van Gaal's side look assured of Champions League football next season but it may not be enough to retain de Gea's shot-stopping services. Juan Mata is the latest United player to be quizzed about the possible transfer. Mata told International Business Times, 'I don't know. To be honest, I don't know. Ask him because I don't know.' If de Gea has not let anything slip to his compatriot, team-mate and good friend, it may be that he is, as yet, undecided about where he will be playing his football next season. Or, he has an inkling but does not want to scuttle his side's push for as high a league standings push as possible. On de Gea's importance to United's season, Mata said, 'Against Crystal Palace [in our 2-1 win], he proved it again with a save that gave us the three points. I wish him to stay. Being selfish, I obviously hopes him to remain with us. He gives us many points.' Meanwhile, Spanish TV station Cuatro caught current Real goalkeeper Iker Casillas on camera as he let rip at whistling, jeering home fans at Santiago Bernabeu during his side's 2-2 league draw with Valencia. Casillas is reported to have proclaimed, 'P*ss off. You are such a drag. F**k. F**k with the sh*tty whistling. F***k off. P*ss off. It's breaking my balls.' We know how you feel Iker. We are often booed in work too.