A fee of £6 million had been agreed between the two clubs earlier today, but the player failed to agree personal terms with the Championship side.
Having played just eight times for the Blues last term, he was loaned to Boro on deadline day in January 2018 and enjoyed a successful spell, making 17 appearances and helping the club reach the Championship play-offs.
Understand Middlesbrough had a bid of £6m accepted for Besic & personal terms were all but agreed, but agent fees caused the breakdown. Boro had multiple bids for Saville & Wallace rejected by Millwall. They still have until end of the month to bring in loans - Bolasie possible.— Keith Downie (@SkySports_Keith) August 9, 2018
Besic was signed by Roberto Martinez in July 2014 from Ferencvaros for £4 million, and his tough tackling and high work rate quickly made him a fans’ favourite.
But following Martinez’s sacking, he suffered an anterior cruciate ligament injury in a friendly against Manchester United in August 2016, ruling him out of the entire 2016-17 campaign.
After returning to action, he found himself some way down the central midfield pecking order, with the likes of Idrissa Gueye, Morgan Schneiderlin and Tom Davies all preferred by both Ronald Koeman and Sam Allardyce last season.
With today’s addition of Andre Gomes on loan from Barcelona, Besic may well now find game time even more limited. Boro could still get the player on loan through till the end of the month, with a buyout clause added for the end of the season.
His Toffees team-mate Cuco Martina may still be joining Tony Pulis’ men, though, having today been linked with a loan move to the north east, as it should be noted Football League teams can still complete temporary transfers until the end of August.