AC Milan stretched their unbeaten run to 12 Serie A games after Riccardo Montolivo's close-range strike proved enough to beat Chievo 1-0 away.
Reacting first after Mario Balotelli's powerful free-kick was spilt by Chievo goalkeeper Christian Puggioni, Montolivo slid in to score the only goal of the game.
It was a bad-tempered game of few chances on a partly waterlogged surface, but second-half Chievo substitute Luciano could have squared the game when his superb drive was tipped over by Christian Abbiati.
Chievo were reduced to 10 men late on when Dario Dainelli was shown a second yellow card.
Having now won eight of their last 10 Serie A games, Milan have been in irresistible form in 2013 and are looking a good bet to pip Napoli to second place. But at a sodden Stadio Marc Antonio Bentegodi, Milan faced a potential banana skin in Chievo, who had won their last two games to pull clear of the relegation zone.
Chances were in short supply for much of the first half as both sides struggled to get to grips with a pitch that had become waterlogged in places. The tackles were flying in, and the game was scrappy, so it was perhaps no surprise that when the deadlock was broken, it came via a set-piece. Moments after an off-the-ball clash involving Balotelli and Bostjan Cesar, the Milan star thumped a free-kick at goal that Puggioni spilled to Montolivo, who reacted quickest and slid the ball in from close range.
Milan continued to test the nervy Puggioni, who struggled with the conditions, with long range efforts and both Montolivo and Balotelli came close before the break.
Chievo showed little quality in attack before or after the break and their best chance fell to substitute Luciano, whose excellent dipping drive from 25 yards was tipped over by the alert and agile Abbiati.
Milan, too, created little in the second half with Balotelli coming closest with a long range free-kick that Puggioni palmed around his post.
Given the conditions and the temperament of the game, it was inevitable that a red card would be brandished at some stage, and Dainelli was the recipient after a needless lunge on Balotelli from behind.
The result leaves the Rossoneri 11 points behind runaway leaders Juventus.