Former AC Milan boss Leonardo, the shock choice to replace the departed Rafael Benitez, takes charge of stuttering champions Inter for the first time in the home clash with second-placed Napoli.
Inter's victory in the Club World Cup in December means they have two games in hand but have slipped down to seventh, 13 points behind leaders Milan.
Leonardo needs a good result against in-form Napoli to silence doubters who still cannot comprehend how a Milan mainstay, far from successful in his one term in charge of the Rossoneri last season, can become coach of their biggest rivals.
"This challenge was too great to resist, and unexpected, and I just couldn't refuse," Leonardo told reporters. "It won't be quite like starting again, because this team is already a reality."
The Brazilian takes over with Inter in better health than they were during Benitez's torrid six-month reign, which ended last month after his public outburst about a lack of signings.
Their injury crisis is all but over, confidence has returned thanks to World Club Cup win and Leonardo has already done one better than Benitez by being given a reinforcement in the shape of Genoa centre-back Andrea Ranocchia.
In contrast to Inter, Leonardo's former team Milan look more brittle than at any time this term and numbers are limited for the trip to coach Massimiliano Allegri's ex-side Cagliari on the bank holiday.
Top striker Zlatan Ibrahimovic is suspended, Alexandre Pato is feeling his way back after over a month out with thigh problems and Robinho needed stitches in his leg after colliding with a television camera in a Dubai friendly this week.
Pato and Robinho are expected to play but with the struggling Ronaldinho seemingly heading back to Brazil, new signing Antonio Cassano is still likely to be called upon despite not looking fully match fit in the Dubai friendly win.
The Italy forward had not played since October, when he was suspended by Sampdoria for swearing at the club president before being sold to Milan now the January transfer window has opened.
Third-placed Lazio travel to Genoa and Juventus, in fourth, have Leonardo Bonucci suspended and Vincenzo Iaquinta out injured for the visit of Parma.
