AS Roma confirmed their return to form with a 2-0 win at Udinese on Saturday to move third in Serie A as Inter Milan fell back into crisis with a 2-0 loss in Genoa.
Inter had looked to have put their poor run going back two months behind them with a 2-1 success against Bologna but the revival was short lived as they suffered a fifth consecutive defeat in Genoa.
Luciano Spalletti's side, who were top of Serie A two months ago and unbeaten until December 16, are now fourth and could fall to fifth if Lazio, who lost last weekend to Genoa, beat Verona on Monday.
Cengiz Under and Diego Perotti scored in the second half in Udine as Roma, with 50 points from 25 games, jump two points ahead of Inter.
Serie A leaders Napoli, who have 63 points, and champions Juventus, one point behind in second, are both in action on Sunday.
Inter defender Andrea Ranocchia turned the ball into his own net for Genoa's first goal on the stroke of half-time with former Inter forward Goran Pandev scoring the second.
"When you go behind at the end of the first half with an episode like that it's not easy, especially in this period, to regain confidence," said Spalletti.
"We are fragile right now and that makes it difficult for us to react to setbacks.
"We have to believe our potential, believing can get us back on track and allow us to stay in the running for the top spots."
Inter were still without injured captain and top scorer Mauro Icardi with Yann Karamoh, who scored the winning goal against Bologna, starting alongside Eder.
Macedonian Pandev threatened early as he pushed visiting goalkeeper Samir Handanovic into two early saves with Genoa counterpart Mattia Perin doing well to clear an Antonio Candreva volley.
But Genoa grabbed the lead on the stroke of half-time when Ervin Zukanovic crossed to Milan Skriniar who slipped with his clearance bouncing off Ranocchia's knee and into his own net.
Pandev doubled Genoa's advantage after 59 minutes, when Oscar Hiljemark's corner was picked up by Diego Laxalt at the edge of the box setting up the former Inter player.
"I always have to thank Inter because they brought me to Italy and I won everything with them, but it was crucial for us to win tonight on front of our fans," said Pandev of Genoa who are in 12th position.
- Under strikes again -
Turkish forward Under, 20, fired home his fourth goal in three games after 70 minutes, with Argentine Perotti tapping in a Radja Nainggolan cross in injury time for Roma.
It was the third straight win for Eusebio Di Francesco's side and a boost ahead of their Champions League clash at Shakhtar Donetsk next Wednesday.
"The team have been improving for the last few games," said Di Francesco who felt they were reaping the benefits of "a psychological as well as a tactical shift".
Perotti added: "It was important that we find our form before the Champions League resumed. Apart from Juventus and Napoli, everyone is dropping points, so we had to win this game before Shakhtar Donetsk."
In an intense first half, both sides had chances with in-form Under shooting just wide while Roma's Brazilian goalkeeper Alisson kept out a Stipe Perica shot.
Roma were denied a penalty when the video assistant referee (VAR) ruled that a handball from Iraqi left-back Ali Adnan, returning after two months out injured, was unintentional.
Perotti came off the bench after 69 minutes with Under opening the scoring a minute later.
And Perotti sealed the victory when converting Nainggolan's cross a minute into time added on.
Massimo Oddo's Udinese stay tenth after back-to-back defeats, missing the chance to pull level with Torino, who host champions Juventus on Sunday.
Chievo earned their first three points since November 25 with a 2-1 win over Cagliari.
Substitute Emanuele Giaccherini had an immediate impact scoring on 74 minutes and setting up Roberto Inglese two minutes later.
The side from Verona are 14th moving ahead of Cagliari who are just behind.
Leaders Napoli host SPAL on Sunday.