John O’Shea returned to the side at the weekend to provide an element of stability to the Sunderland back line but after completing the signings of Younes Kaboul, Adam Matthews and Sebastian Coates, Advocaat seems keen to bring in further reinforcements at the back.

Manchester City starlet Jason Denayer is nearing a loan move to Turkish champions Galatasaray, according to Belgian journalist Kristof Terreur.

After being promoted to Manchester City’s senior side, Denayer spent a fantastic 2014-2015 season on loan at Celtic, where he was a key part of the team’s conquest of the Scottish Premiership, winning the PFA Scotland Young Player of the Year award.

Who should Sunderland sign before the end of the window?

Advocaat remains desperate to boost Sunderland’s options up front and in midfield, with the club due to learn if ex-Swansea man Jonathan de Guzman is willing to return to the Premier League on loan from Napoli.

Denayer is not third choice now either, with Martin Demichelis on the fringes of the team and Nicolas Otamendi having signed for the Citizens for £32.5 million last week.

The 20-year-old defender netted six times and provided two assists in 44 appearances for Celtic in all competitions last season.

Sunderland are not alone when it comes to being interested in the 20-year-old, however.

He said: “We need two or three to strengthen positions to get more competition in the squad”.

“You need competition during the games, but also in training, so they don’t feel it’s easy”.