Thiago Silva added a fourth in the 58th minute to keep the reigning champions ahead of second-placed Juventus who dropped points at home to Chievo .

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The form of Paris Saint-Germain defender Thiago Silva and the return to the side of Real Madrid's Kaka had looked to have given Brazil a new found lease of life.

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In the summer the Rossoneri had slashed their wage bill by 35%, letting go a number of veterans and selling their best attacker (Zlatan Ibrahimovic) and their best defender (Thiago Silva).

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But the move fell through and PSG moved on to other targets, landing striker Zlatan Ibrahimovic and AC Milan teammate Thiago Silva as well as Napoli winger Ezequiel Lavezzi and Brazilian prodigy Lucas.

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Last summer Milan owner Silvio Berlusconi decided that the team could no longer operate beyond its means and sold off the crown jewels in the shape of Thiago Silva and Zlatan Ibrahimovic to PSG.

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Fellow Brazilian international Thiago Silva defended him.

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Siena battled on gamely, and on 26 minutes Massimo Maccarone escaped three defenders on the edge of the Milan box to bundle through before firing over on the stretch as Thiago Silva came across to put him under pressure.

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Thiago Silva almost made it 2-0 three minutes from the end when he headed against the crossbar from point-blank range, and Borriello killed off any doubt with a spectacular volley from Ronaldinho's cross three minutes into time added on.

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Eleven minutes from time, Ibrahimovic -- who signed a five-year deal with Barcelona in 2009 but whose spell at the Nou Camp was so unhappy he left after just twelve months -- converted from close range, despite being in an offside position, as he reacted quickest to a towering header against the post by the outstanding Thiago Silva.

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