Muhamed Besic's transfer to Middlesbrough has collapsed due to a disagreement over agent fees.
The 25-year-old looked set to rejoin Boro from Everton after spending the second half of last season on loan at the Riverside.
A £6million fee had been agreed as well as personal terms, only for the deal to stall at the final hurdle, according to Sky Sports.
Besic could still sign for Boro on loan before August 31 but a permanent deal is now off.
The news explains why Boro launched a late bid for Millwall duo George Saville and Jed Wallace, which was rejected before the 5pm deadline.
Clubs can still sign players up until 7pm, providing they have submitted a 'Deal Sheet'.
Besic was arguably Boro's standout midfielder in the second half of last season after arriving in January.
It came after the Bosnian had fallen out of favour at Goodison Park following an injury-hit spell on Merseyside, where he still appears to be surplus to requirements.
Besic made 17 appearances for Boro last campaign, while his ability to break up play and run with the ball was fundamental to Tony Pulis' side.
The Boro boss also missed out on Everton winger Yannick Bolasie, with the Toffees only willing to selling the winger on a permanent deal.