AC Milan wasted the latest in a series of chances to boost their Serie A title hopes when a depleted side were held 1-1 at home by Lazio on Sunday.
AS Roma beat leaders Inter Milan 2-1 on Saturday to cut the gap at the top to a point but Milan remain third rather than moving level with the Romans after another unconvincing display.
"This is a strange championship. There are lots of surprises," Milan coach Leonardo told Sky TV with seven games left. "I think the team did well. We conceded an unlucky goal."
Shortly after Clarence Seedorf had been denied following a fine move, Mathieu Flamini collided with Aleksandar Kolarov as he burst into the box and the referee awarded a soft penalty.
Marco Borriello, standing in as penalty taker with Ronaldinho suspended, converted from the spot on 18 minutes despite keeper Fernando Muslera getting a hand to the ball.
Milan, beaten at Parma on Wednesday, struggled to create other chances with Andrea Pirlo also suspended and were pegged back when Luca Antonini failed to clear a cross and Swiss winger Stephan Lichtsteiner scrambled in the leveller on 32 minutes.
Lowly Lazio, whose fans could be in trouble after racist chants towards Seedorf, had won two in a row but Milan will be kicking themselves yet again given Antonini hit the bar.
Felipe Melo earlier gave protesting Juventus fans a rare reason to cheer after heading the winner eight minutes from time in a 2-1 home victory over third-from-bottom Atalanta.
Supporters, angry the famous club is struggling to reach the Champions League next term, threw eggs at the team bus as it arrived at Turin's half-empty Stadio Olimpico and unpopular right back Jonathan Zebina was then jostled.
Juve's Alessandro Del Piero bent in a sublime free kick on half an hour after his side had made another laboured start, although David Trezeguet had a header ruled out for offside.
The hosts, who have made no marked improvement since Alberto Zaccheroni replaced Ciro Ferrara as coach in January, paid for their lacklustre approach when former striker Nicola Amoruso was left in space in the area to comfortably equalise on halftime.
Substitute Melo, ridiculed by fans as the latest expensive signing to flop, then nodded in Del Piero's cross.
Atalanta, who had won their last two games to raise hopes of escaping relegation, could easily have scored again having exposed Juve's shaky defence several times in both halves.
Juve, Napoli and Sampdoria are all three points behind Palermo, who occupy the fourth and final Champions League qualifying spot having beaten Bologna 3-1 on Saturday.
Napoli overcame Catania 1-0 at home thanks to Paolo Cannavaro's goal but Samp missed the chance to hold fifth spot alone when they were held 1-1 at home by Cagliari.
At the bottom, Livorno look doomed after a 1-1 home draw with Bari left them seven points away from safety.
Second-from-bottom Siena dominated Genoa but drew 0-0 and lie six points behind fourth-from-bottom Udinese, who were hammered 4-1 at Fiorentina.