Lazio notched up their fourth away win in a row after beating hosts Palermo 1-0 on Sunday to move four points clear at the top of Serie A.
The only goal came at the 27th minute when Defender Andre Dias scored with a superb volley from a free-kick and the visitors were on the back foot for most of the match.
Antonio Cassano was dropped by Sampdoria after he swore at the club's president last week, and his team-mates fought hard to secure a last-gasp 1-0 victory at Cesena thanks to a goal from Giampaolo Pazzini.
As Milan lost to Juventus 2-1 on Saturday, Lazio, relegation candidates last term, would stay top whatever the result in Sicily, and Palermo made them sweat with relentless pressure.
The highly rated Argentinian playmaker Javier Pastore had missed a good early chance for the hosts and almost scored when Lazio goalkeeper Fernando Muslera struck a clearance against him.
Palermo continued to dominate in the second half after Lazio's Giuseppe Biava was dismissed for a second yellow card after 77 minutes, but Muslera and his defence held out to leave Lazio on 22 points from nine games.
Next weekend Lazio face their city rivals Roma, who will be without their captain Francesco Totti after he was sent off in Roma's 2-0 win over Lecce on Saturday.
While Lazio hope to sustain an unlikely title challenge with a modest squad, Sampdoria are poised to play without their banished talisman Cassano for the foreseeable future. They missed his creative ideas in victory at Cesena, where Pazzini grabbed the winner in injury time.
Cassano, who had appeared to have outgrown his bad-boy image, was dropped and disciplinary proceedings were brought against him after he swore at the club's president, Riccardo Garrone.
The Italy forward, whose Azzurri future is also unclear if he does not play, has apologised, but whether he will be sold in January or brought back into the fold remains to be seen.
The Argentinian striker Ezequiel Lavezzi scored a second-half goal to give Napoli a 1-0 win at Brescia in heavy rain to lift the visitors to fifth in the table.
In other games, Udinese continued their rise up the table with a 2-0 win at the bottom side Bari. Their fellow strugglers Bologna lost 2-0 at Cagliari and Parma drew 0-0 with Chievo.