Zlatan Ibrahimovic failed to inspire AC Milan to victory on his return to the club after emerging from the bench in a 0-0 draw with Sampdoria at the San Siro.
The former LA Galaxy striker signed a six-month contract with Milan, whom he played for between 2010 and 2012, last month and was named as a substitute on Monday.
Ibrahimovic replaced Krzysztof Piatek for the final 35 minutes – 2,794 days since his last Serie A appearance on 13 May 2012 – but could not find a winner for the hosts.
The 38-year-old had two chances to break the deadlock but saw one header well saved by Sampdoria goalkeeper Emil Audero and another effort cleared off the line.
⏱ 55'@Ibra_official comes on to replace @pjona9official / Entra Ibra per Piątek#MilanSampdoria 0-0 #SempreMilan pic.twitter.com/pl9DPqp1Pv — AC Milan (@acmilan) January 6, 2020
Cristiano Ronaldo scored his first Serie A hat-trick as second-placed Juventus ran out 4-0 winners over Cagliari.
The Portugal captain pounced on a mistake from Ragnar Klavan to open the scoring just after half-time for the hosts.
Ronaldo then converted a 67th-minute penalty after Paulo Dybala was fouled in the area and Gonzalo Higuain added a third in the 81st minute.
The final act was left to Ronaldo, though, who slotted under the onrushing Robin Olsen to take his Serie A tally for the season to 13 in the closing stages.
⚽️ 49'⚽️⚽️ 67'⚽️⚽️⚽️ 82'#JuveCagliari #CR7JUVE pic.twitter.com/58t1v6KcHZ — JuventusFC (@juventusfcen) January 6, 2020
Inter Milan maintained their place at the top of Serie A with Romelu Lukaku scoring twice in a 3-1 win at Napoli.
The former Manchester United forward netted two breakaway first-half goals to keep Antonio Conte’s side above Juve.
Lukaku ran 60 yards and fired home left-footed for his first in the 14th minute and was then thankful for a howler from Napoli keeper Alex Meret after 33 minutes.
Arkadiusz Milik pulled a goal back for the hosts six minutes later before Lautaro Martinez restored Inter’s two-goal advantage just after the hour mark.
This pair now have 3⃣0⃣ goals between them this season. A strike partnership of dreams 💭#NapoliInter #ForzaInter ⚫️🔵 pic.twitter.com/CC7Dtepw2x — Inter (@Inter_en) January 6, 2020
Josip Ilicic scored twice as Atalanta kept up their pursuit for Champions League qualification with a 5-0 victory at home to Parma.
Papu Gomez, Remo Freuler and Robin Gosens gave the Nerazzurri a 3-0 half-time lead before Ilicic added a second-half double.
Riccardo Orsolini’s added-time equaliser rescued a 1-1 draw for Bologna at home to Fiorentina, who had led courtesy of Marco Benassi’s 27th-minute goal, while Rodrigo De Paul’s late winner earned Udinese a 1-0 victory at Lecce.