Dumped out of the Champions League last week by Deportivo La Coruna, Milan showed their determination not to let their European hangover affect their championship challenge by grinding out a narrow victory in rainy Tuscany.

Andrei Shevchenko put Milan ahead from close range with his 21st league goal of the season, before giving away the penalty from which Enrico Chiesa levelled the scores.

Siena's Simone Vergassola was sent off for kicking out at Kaka in the 79th minute before Milan's gifted South American added insult to injury by grabbing the decisive goal.

With four matches left to play, Milan have a 12 point lead over second-placed Roma, who have two games in hand on the league leaders and play away to Modena on Sunday.

Defeat for Siena, who were playing Milan in Serie A for the first time in their history, kept them seventh from bottom.

Lecce moved up one place and level with Siena on 31 points after they came from behind to defeat Udinese 2-1 in Puglia.

Uruguayan striker Ernesto Chevanton was Lecce's hero, grabbing the winner five minutes from time for his 16th goal of the season.

Milan's victory saw them set a new record for the most number of points taken from away matches in a Serie A season.

Milan, unbeaten on the road, have amassed 37 points from their 15 away games, two more than the previous record set by Juventus in the seasons 2000/1 and 1994/95.

Milan coach Carlo Ancelotti said it would have been an injustice had his team not clinched all three points.

"When Siena were left with 10 men our chances certainly improved, but I thought that overall we had done enough for the victory," he said.

Milan vice-president Adriano Galliani said a second consecutive win helped ease the painful memory of their 4-0 defeat to Deportivo in the quarter-final of the Champions League 10 days ago.

"The Scudetto isnt sown up yet, but this was a very important step towards it and the team played very well," he said. "The team has shown great character after going out of Europe."

Milan looked sharp in the early exchanges even without injured strikers Fillipo Inzaghi and Jon Dahl Tomasson and almost opened the scoring in the ninth minute.

Kaka carved his way through the Siena defence and set up Shevchenko whose neat cutback was intercepted by the outstretched boot of Leandro Cufre.

Chiesa tried his luck from long range but failed to trouble Milan keeper Dida before the visitors took the lead in the 26th minute.

Marcos Cafu broke down the right and crossed for Manuel Rui Costa whose left-footed drive was too hot for Siena keeper Marco Fortin to handle and Shevchenko pounced to ram home the rebound.

Three minutes later the Ukrainian could have doubled his tally when he met Cafu's cross with a bullet header, but this time Fortin got a firm hand behind it.

Shevchenko went from hero to villain seven minutes from half-time, though, when defending a Chiesa free-kick.

The former Dinamo Kiev player raised his elbow which prevented the ball from clearing the wall and referee Pierluigi Collina pointed to the spot.

Chiesa smashed his spot-kick past Dida to draw Siena level with his ninth goal of the season.

Shevchenko's angled shot rolled agonisingly wide as Milan took the game to Siena in the second half before Italy under-21 international Marco Borriello was given a rare appearance in place of Rui Costa.

Vergassola saw red for his second yellow card 11 minutes from the end and less than 60 seconds later Kaka settled the match.

Andrea Pirlo's right-wing corner kick was nodded across the face of goal by Borriello and Kaka flung himself forward to head past Fortin from six yards out.