Milan's Sunday night win -- their fourth in five matches -- lifted them to the seventh spot with 34 points -- three behind Sampdoria, who moved to four short of fifth-placed Roma.
While Milan cut short Lazio's high-flying six-game streak without a loss, Sampdoria's win extended Roma's five-match winless streak.
Sampdoria rode on Duvan Zapata's 80th-minute strike to gain three points at the capital's Olympic Stadium.
Roma rued a missed penalty after Sampdoria blocked Alessandro Florenzi's spot-kick in the 39th minute.
"Certainly, if we had scored (the penalty) it would have changed the game and, of course, I take all the responsibility for that. I got it wrong, unfortunately, but it's happened now," Florenzi said, according to Roma's website.
"We certainly tried to make up for it after, but unfortunately at the moment we are in a bit of a tunnel and we can't see the light. We absolutely need to turn things around, as we have done in the past. We created a lot of chances once again tonight, but we need that little bit of good fortune. And it has to come soon."
In Milan, after a very negative first half of the season, the hosts managed to get their act together at the San Siro Stadium, reports Efe.
Lazio were the better team throughout the match, but were unable to bring things to fruition and lost a golden opportunity to strengthen their third-place position with 46 points.
AC Milan managed to get on the board 20 minutes into the match, when Patrick Cutrone took advantage of a free kick by Turkey's Hakan Calhanoglu for his third goal of the year.
Lazio didn't delay in responding, however, with Serbia's Adam Marusic tying things up just five minutes later on an assist from Brazil's Lucas Leiva and a left-footed shot.
Just five minutes before the break, however, the Gennaro Gatuso-coached home squad made it 2-1 with Giacomo Bonaventura heading in a cross from Davide Calabria, beating goalkeeper Tomas Strakosha.
After the break, Lazio created shooting chances but never managed to sink one and the score remained fixed delivering three points to Milan and keeping them undefeated since 1989 against Lazio at San Siro in the competition.
"This was a very tough test as we played a strong side. They pressured us so much in the second half, they are good in everything; yet, we won and the credit goes to the boys," coach Gattuso was quoted as saying by AC Milan's website.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
