Middlesbrough manager Tony Pulis.

From an ex-Manchester United striker to Chelsea's captain: Out-of-contract players who Middlesbrough could sign this summer

With 12 games to go Middlesbrough's promotion hopes remain in the balance - yet discussions will already be talking place regarding next summer's transfer business.

Although a large part of Boro's business will depend on which division they find themselves in come the end of the season, those behind the scenes will already have one eye on potential targets. The free agent market proved successful for the Teessiders earlier this year following the capture of ex-Chelsea midfielder John Obi Mikel - but could Boro profit again? We take a look at some players whose contracts are set to expire this summer. Scroll down and click through the pages to look at some of the players who may be available:

While Boro appear well stocked in centre midfield, the Iceland international is a fierce competitor. Gunnarsson, 29, has been a regular for Cardiff in the top-flight this term and possess a threat with his long throws.

1. Aron Gunnarsson (Cardiff City)

While Boro appear well stocked in centre midfield, the Iceland international is a fierce competitor. Gunnarsson, 29, has been a regular for Cardiff in the top-flight this term and possess a threat with his long throws.
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The Crystal Palace midfielder, 32, was linked with Boro in the summer but remained at Selhurst Park. He has since joined Huddersfield on loan but could be available at the end of the season.

2. Jason Puncheon (Crystal Palace)

The Crystal Palace midfielder, 32, was linked with Boro in the summer but remained at Selhurst Park. He has since joined Huddersfield on loan but could be available at the end of the season.
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Boro's lack of pace and power in wide areas has been an issue all season. Sako possess both in abundacne but has struggled for game time on loan at West Brom this term.

3. Bakary Sako (Crystal Palace)

Boro's lack of pace and power in wide areas has been an issue all season. Sako possess both in abundacne but has struggled for game time on loan at West Brom this term.
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Simpson has fallen down the pecking order at the King Power and has made just five top-flight appearances this term. Now 32, it seems likely the Premier League winner will be looking for a new club this summer.

4. Danny Simpson (Leicester)

Simpson has fallen down the pecking order at the King Power and has made just five top-flight appearances this term. Now 32, it seems likely the Premier League winner will be looking for a new club this summer.
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