Milan - The Serie A ambitions of Roma and Milan face the acid test as the second half of the season begins with champions and leaders Juventus looking unstoppable in their quest for a fourth consecutive league title.
Roma travel to a resurgent Fiorentina on Sunday desperate not to lose more ground in the race for a first scudetto since 2001, having dropped five points behind Juve following a second consecutive draw last week, away to Palermo.
Since the departure of striker Gervinho to the Africa Cup of Nations a fortnight ago, Rudi Garcia's title challengers have lacked the bite usually provided by the feisty Ivorian, and Juventus have capitalised.
Juventus are unbeaten since a 1-0 away reverse to Genoa in October and host struggling Chievo in Turin looking to make it three wins on the trot.
Garcia insists Roma's absences are not a problem, telling La Gazzetta dello Sport: "We have a large and quality-packed squad, so the absences are not too much of a problem for us."
Juventus striker Fernando Llorente insisted to Sky Sport: "Roma are a great team, we know they want to win the scudetto and we can't allow ourselves to ease off."
But cracks have begun to appear in Garcia's side, and Fiorentina are expected to push Roma all the way in Florence.
Roma owed their midweek qualification for the quarter-finals of the Italian Cup to a dubious late penalty which gave them a 2-1 last 16 win over furious Empoli.
Fiorentina, meanwhile, had Mario Gomez and Juan Cuadrado to thank for a 3-1 win over Atalanta at the same stage of the competition, when Micah Richards made a notable contribution as part of a solid Viola back four.
Fiorentina have climbed to sixth in the table and Cuadrado -- a reported target for Premier League giants Chelsea -- insisted: "I'm 100% available and we'll work hard to prepare for the match."
Struggling Milan, meanwhile, can ill afford to drop points against Lazio a week after a shock 1-0 home defeat to Atalanta blew a hole in their Champions League qualifying hopes.
Success as a coach is not coming easily for Filippo Inzaghi, one of Milan's most prolific strikers in his day, having seen his side whistled off the park at the San Siro last week.
Ahead of meeting a Lazio side desperate to make amends for last week's 1-0 home reverse to Napoli, Milan sit 20 points behind Juve and seven behind Napoli in the third and last Champions League qualifying spot.
Inzaghi and defender Philippe Mexes have both launched a rallying call: "It's down to me to turn the whistles into applause. We simply have to roll up our sleeves and do more."
"We need a good result against Lazio and to play well to try and restore confidence," said Mexes.
City rivals Inter are also 20 points off the pace but host Torino at the San Siro confident of a win after a stirring 2-0 Italian Cup victory over Sampdoria.
Swiss international Xherdan Shaqiri scored his maiden Inter goal on his full debut, earning the praise of coach Roberto Mancini, although the Italian said he is still waiting for a more "compact" Inter to do more damage.
"Shaqiri's class and personality was clear for all to see. I'm happy that he and (Lukas) Podolski had such a good game," said Mancini.
"I think we can do even better though. Once the team is more compact they'll be able to play with even more quality."