ANDY O'BRIEN fears Newcastle United could cash in on him this summer after being shocked by the departure of Aaron Hughes to Aston Villa.

O'Brien only signed a new contract towards the end of last season but realises that counts for little if manager Graeme Souness decides to sell.

Prior to Christmas it was O'Brien who was linked with a possible move to Villa Park but, last week, it was Hughes who was snapped up by David O'Leary.

The centre-back, currently on duty with the Republic of Ireland, played a part in Jackie McNamara's testimonial game at Celtic last night and said he was sad to see his team-mate go.

But he realises that Souness must have his reasons for allowing the versatile and likeable defender to leave in a £1.4m deal.

O'Brien said: "I'm disappointed Aaron has left the club. First and foremost he was my room mate and we are good friends. I don't think there's any doubt he will be a big loss to the club.

"He's been a fantastic professional and a big favourite with the fans. It's sad to see him go, he will take some replacing.

"There's been plenty of talk during the last few weeks that players will be leaving and new players will be coming in but losing Aaron was a surprise.

"Every player thinks about his situation in the close-season and every player has a price. You're never certain what the future holds.

"I'm no different but I've been told to report for pre-season training and that's what I'll be doing. Last season was difficult and disappointing but the players want to put things right."

Instead of taking a break from the game O'Brien has been on duty with the Republic since the beginning of the week ahead of World Cup qualifiers with Israel (June 4) and the Faroes Islands (June 8).

He feels not having a rest will ensure he keeps fit and focused for the new campaign with Newcastle.

"I'm feeling fine and I'm keen to play a key role in the World Cup qualifiers. It's strange returning to full training so soon after the end of the domestic season but it doesn't take much to get back into shape," he said.

"People talk about this time of year as the close-season but for those players involved in World Cup qualifiers it's a hugely important time of the year.

"England have decided not to play competitively this summer but I'd rather be playing for something than playing friendlies. I've been focused on these games since the end of Newcastle's season and I can take my holiday later."

Meanwhile, O'Brien's international team-mate and Newcastle target Robbie Keane is refusing to rule out the prospect of a summer move to Celtic - particularly in light of Gordon Strachan taking over the Parkhead helm on June 1.

Keane appears to have dropped down the Spurs pecking order under Martin Jol and, with just a year remaining on his contract, speculation is mounting over his future.

Keane said: ''I have been linked with moves to every club this summer.

''At the end of the day, I've got one year left at Tottenham, and I am happy there but, if things change, then who knows? If the manager or chairman came to me and told me I was no longer wanted at Spurs then I am going to have to consider my future.

''As I have said, I am a Celtic fan, and I have also said that one day I would like to play for them.''

Talking of Strachan, Keane added: ''He's the best manager I have worked under because he gets the best out of players.

"He has this enthusiasm for the game and he knows the game inside out."