Marcel Desailly's 28th-minute goal, his first since leaving Marseille in November, proved sufficient to end Reggiana's unbeaten home record. The hosts' defence failed to clear a corner from Roberto Donadoni and Desailly seized on the loose ball to score.
Milan lead the table with 25 points from 16 matches, two clear of Juventus and Sampdoria, who have both played a game more.
Milan travel to struggling Udinese next Thursday but are already assured of finishing the first half of the 34-match campaign on top of the table - as they have done in the previous two championship-winning seasons.
The new European Footballer of the Year, Roberto Baggio, started 1994 impressively, leading Juventus to their first away win of the season with two goals in a 3-0 win at Udinese. In the 11th minute, his perfectly weighted pass gave Giancarlo Marocchi time and space to score with a finely angled shot. Three minutes into the second half, goalmaker turned goalscorer as Baggio's cheeky backheel from a cross by Angelo Di Livio found the net via a deflection. The prolific playmaker took his season's tally to 11 in the 61st minute, slaloming through Udinese's defence and sliding the ball past Graziano Battistini.
Parma dropped to fourth in the table with a 1-1 draw at Piacenza while an 87th-minute goal from Pierluigi Orlandini earned Atalanta a surprise 2-1 win over Internazionale at the San Siro stadium.
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