Substitute Alberto Paloschi struck the crucial goal 19 minutes into the second half - just moments after his introduction - as Carlo Ancelotti's team consolidated fifth position in the Serie A standings.

Siena were reduced to 10 men eight minutes from time when Simone Vergassola saw red.

Zeljko Kalac - currently keeping Dida out of the Rossoneri first XI - did his chances of keeping hold of the number one jersey no harm at all with another clean sheet.

The 35-year-old Australian, nicknamed 'Spider' for his lanky appearance, set up the Diavolo's first attack in the sixth minute when his goal-kick led to a counter-attack which ended with his opposite number Alex Manninger deflecting an Andrea Pirlo effort out for a corner.

Alessandro Nesta thought he had put the Rossoneri ahead after 12 minutes when he beat Manninger from Cafu's free-kick, but play was called back for offside.

The hosts continued to push forward and, three minutes later, Massimo Ambrosini fired over on the rebound after Filippo Inzaghi's left-footed effort had been blocked by the Robur defence.

Ronaldo - starting up front alongside Inzaghi in the absence of Kaka and Alexandre Pato - then cut inside on the edge of the area but slipped at the vital moment and lost possession before being able to get a shot away.

Pirlo was next to have a go midway through the first half but his right-footed shot from 20 yards flew over the crossbar.

Kalac was called into action for the first time just before the half-hour mark when he got down well to keep out a drilled free-kick from Lucas Jarolim.

Ronaldo had another sight of goal in the 31st minute but saw his right-footed shot from 12 yards blocked by Simone Loria.

At the other end, Serginho cleared the danger from the Milan area before Mario Frick could get to it and the teams went in at the break on level terms.

The deadlock was finally broken shortly after the hour mark when Paloschi - brought on in place of Serginho a minute earlier - hit a left-footed shot which went in off Manninger's right-hand upright.

Three minutes later, Paloschi twice almost doubled his tally. First his long-range effort was blocked by Manninger and then, from the rebound, the substitute hit the post.

The visitors' cause was not helped eight minutes from time when Vergassola was shown a straight red card for handball on the edge of the area to deny Inzaghi a chance.

Despite their man disadvantage, Frick was presented with a fine chance to equalise for Siena two minutes from time but his header from eight yards was brilliantly tipped over the bar by Kalac for a corner.