Roma vs. Inter isn't quite the top-of-the-table clash that it has been in recent seasons, but it's a fixture that's still vital to both clubs.
The Giallorossi can't afford to drop points if they want to maintain their slim chance of catching Juventus, while the Nerazzurri will want to make every game count if they're to stay in fifth, just ahead of this year's surprise package, Hellas Verona.
There's also the prospect that Fiorentina, ahead of Inter by five points, could drop points to Edy Reja's Lazio. And with Juve facing Clarence Seedorf's resurgent Milan at the San Siro, Roma could steal a march by winning, too.
With so much at stake, what will be the key battles to watch in this game?
Roma's Rudi Garcia is without Francesco Totti, Federico Balzaretti, Dodò, Maicon and Alessandro Florenzi. Vasilis Torosidis and Gervinho are serious doubts, so the Giallorossi are without a slew of key first-team personnel.
With this is mind, Garcia will likely be forced into a slight formation change, playing Miralem Pjanic as an attacking midfielder ahead of his traditional midfield triangle and a pair of forwards. The line-up should look like this (4-3-1-2): De Sanctis, Torosidis, Benatia, Castan, Romagnoli, Nainggolan, De Rossi, Strootman, Pjanic, Destro, Ljajic.
Tactically, that shouldn't cause Roma any problems because the front three will all still be comfortable with the shift and it doesn't affect the rest of the squad's shape.
Inter should be welcoming January's marquee signing, Hernanes, into the fore, but with the Brazilian lacking match fitness, it will be interesting to see if he lasts the 90 minutes in Mazzarri's 3-5-2.
The Nerazzurri should look something like: Handanovic, Juan Jesus, Samuel, Rolando, Nagatomo, Hernanes, Kuzmanovic, Guarin, D'Ambrosio, Icardi, Palacio.
Without the likes of Gervinho, Maicon and Florenzi, Roma should look quite different for this game. The Lupi have been excellent out wide this season, but injuries have forced a change in formation and it's unlikely that they'll be doing their best work along the touchline against Inter.
Adem Ljajic can ostensibly play in a wide position, but the Serbian is no winger and does his best work cutting inside. The midfield of Daniele De Rossi, Radja Nainggolan and Kevin Strootman will look to spread themselves around, but none of that trio are true wide players either.
From a Roma perspective, then, the hope will be that they'll be tactically astute enough, and good enough going forward, that young Alessio Romagnoli won't be left too exposed at full-back. The young Roman is a great prospect, but lacks experience in these kind of crucial games and will need to be protected.
For Inter fans, it will be interesting to see what new signing Danilo D'Ambrosio and Yuto Nagatomo can do against this more centrally-focused Roma. Both are capable of getting forward and into dangerous positions, but the Giallorossi's formidable centre-back pairing of Castan and Mehdi Benatia will mean that the Nerazzurri's forwards will need to bring their A-game if they want to capitalise on any good work their wing-backs might do.
Without the colossal presence of Francesco Totti, this is a game for several of Roma's young forwards to prove their worth.
The Giallorossi captain's performances are usually so influential that there's a danger his younger counterparts can either be overshadowed—or allowed a place to hide.
There'll be no such shield in this game. Unleashing Pjanic as a proper trequartista should allow the Bosnian to shine as his side's main creative influence, while farther forward the young pairing of Ljajic and Mattia Destro will be in full view, with neither Totti or Gervinho to lean on for goals.
Destro has been a joy to watch since coming back from injury, and on this form he'll have one eye on a place in Cesare Prandelli's squad for the World Cup this summer. He's up against some stiff competition for that, so games like this, where he is Roma's No. 1 goal threat, are vital.
It will be interesting to see if Inter can cope. At 35, Walter Samuel isn't quite "The Wall" he used to be, and it's hard to see him keeping up with the pace and the intelligence that are hallmarks of Roma's attacking play.
Ahead of him, ex-Lazio man Hernanes will be used to dealing with Roma, but Zdravko Kuzmanovic is a liability and Roma's midfield—currently making a case for itself as one of the best in Europe—is more than a match for that pairing and the excellent Fredy Guarin. Mazzarri will want to stop that Roma midfield trio storming forward to supply the forwards, but as the rest of Serie A will tell him, it's easier said than done.