Arsenal continued to negotiate with Real Madrid on Monday over the signing of Nuri Sahin, with the sticking point being what may happen to the midfielder at the end of his proposed season-long loan at the Emirates Stadium.

Arsène Wenger, the Arsenal manager, wants the option to make the transfer permanent but Madrid are reluctant effectively to sign over his rights, in case Sahin were to find exceptional form.

The 23-year-old Turkey international left Borussia Dortmund for Feyenoord on a season-long loan in 2007-08 and the move ignited his career. Feyenoord had no option to buy.

Wenger has long admired Sahin but he has followed him particularly closely this summer as Alex Song edged towards the Arsenal exit. Song has completed a £15m transfer to Barcelona, having undergone a medical on Monday, to leave Wenger with a vacancy in midfield, although the manager did say after Saturday's goalless draw against Sunderland that he is happy enough with the midfield options at his disposal.

He mentioned Abou Diaby and also noted that Jack Wilshere and Tomas Rosicky were on their way back from injury. Arsenal are always cautious when talking about transfers and they do not like to get ahead of themselves.

Madrid have made it clear that they are receptive to the notion of loaning Sahin, with José Mourinho, the Madrid manager, telling him at the beginning of the month that "if you decide to leave, we are going to help you to leave". Sahin moved to Madrid from Dortmund for €10m (£7.8m) last summer but his impact in La Liga was minimal as he struggled in the face of the competition for places from Xabi Alonso, Sami Khedira, Mesut Ozil, Lassana Diarra and Esteban Granero.

Liverpool have attempted to sign Sahin this summer although unlike Arsenal, they do not have Champions League football to offer.

Sahin, a highly technical, deep-lying playmaker, would not appear to be a like-for-like replacement at Arsenal for the imposing Song, even if the Cameroonian is a more creative player than he is sometimes given credit for. He supplied 14 assists in all competitions last season.

Song has departed under a cloud, with his desire to listen to Barcelona's proposal and, latterly, to push for it setting him at odds with Wenger and leading figures at the club, who felt that they deserved greater loyalty. Song's view of his worth to the team also differed from that of Wenger. Arsenal readily accepted Barcelona's bid and there has been the suggestion that Song, because of his highly individual streak, was a bad influence in the dressing-room.

Song feels that any attempts to discredit him have been borne out of Arsenal's need to give the fans an explanation. He believes that he has nothing to prove and the fact that he has joined Barcelona speaks for itself. Arsenal did, though, post a supportive message on their website when they confirmed that the transfer had been completed.

"Everyone at Arsenal would like to thank Alex for his contribution to the club and wish him the best of luck for the future," it read.