Edy Reja returned to the Lazio bench with a win against Inter. The Aquile welcomed the Nerazzurri to the Stadio Olimpico in Rome having won just twice in their last 12 games, but managed to grab an unlikely victory thanks to a late volley from Miroslav Klose.
The home side were far from brilliant, but the visitors did little to test them and in the end limped to a disappointing loss that now leaves them in sixth, eight points off the final Champions League spot.
What did we learn?
Inter were below par at the Stadio Olimpico, but in truth neither side looked up to much.
As seems to be the tradition in football, Lazio responded to having a new manager on the bench by working hard and grinding out a win, but there was little on show to suggest that Edy Reja's version of the Aquile will be any better than that of Vladimir Petkovic.
Reja has a serviceable squad at his disposal, but the poor manner in which they've performed this season says a lot about their mentality, just as the sacking of Petkovic tells you plenty about owner Claudio Lotito's thinking.
The Bosnian-born Swiss coach worked wonders last year, crafting a hard-working side out of a bare-bones squad, working with on a little budget, and went on to win a historic Coppa Italia final against local rivals Roma.
It's been a tougher season this time around for Lazio, but the coach was better than results suggested, and after the success of 2013, deserved a chance to prove it.
Inter survived until late on, but could have gone down in the first half to a great chance for Senad Lulic, when the Bosnian took advantage of confusion in the Inter box to make a lofted attempt at goal.
The goal eventually came from Antonio Candreva's fine cross from the right wing, which was met by a lovely half-volley from Miroslav Klose in the 81st minute.
Both chances would have been snuffed out by a more organised defence. Samir Handanovic is a fine goalkeeper, but there's only so much he can do when those in front of him are either confused or just not good enough.
Some work can be done on the training ground, but at this stage it's becoming clear that for a genuine improvement, purchases will have to be made as soon as possible.
Etrit Berisha must have thought his birthday came early against Inter. The young Albanian was making his Serie A debut for Lazio in place of the injured Federico Marchetti, not an ideal fixture for a debutant because the Nerazzurri have been the most potent Italian side in front of goal this season.
Instead of the usual beating from Rodrigo Palacio & Co., however, Berisha was treated to a reasonably calm evening between the posts at the Olimpico. And that should worry Inter fans.
It's obvious the the squad needs improvement, but the positive of the season so far has been that Inter haven't been goal-shy. The efficiency of the forwards has often papered over the cracks elsewhere, but if they stop scoring Mazzarri will be in real trouble, really quick.
The coach will be hoping that Palacio just had an off night and that Diego Milito—who finally made a return to first-team duties—can find form quickly.
Reports that Fredy Guarin is on his way out of the San Siro have been circling for some time, but it's now clearly more than rumour because the club have admitted contact with interested clubs.
Guarin's ability is sometimes overstated, and the Colombian is not the answer to all of Chelsea's problems, but he is a fine player and not one that the Nerazzurri can afford to let go. Against Lazio he was one of the few Inter players who mustered anything creative, and if he leaves he'll be a big loss.
This isn't exactly something we've "learned" as much as it is something that seems to be reinforced with each appearance. How Andrea Ranocchia manages to get a game for Inter or for Italy is anyone's guess, but it's time that Mazzarri looked for another option.
None of Inter's back-line covered themselves in glory against Lazio, but the 25-year-old Ranocchia was particularly bad. He was totally asleep when Lulic almost scored and was completely to blame for Klose's winner. The German striker exposed him for what he is—an average defender who's easily outsmarted. Inter deserve better.
Reja and Mazzarri play different systems, and there's little doubt who most fans would rather have on their bench, but the Tuscan will have been a little jealous of his 68-year-old counterpart after this game.
Lazio were far from brilliant, but their players outshone their Nerazzurri counterparts in all the key areas—and that will frustrate Mazzarri.
The Inter defence was poor, while the Lazio back-line was alert and well organised.
Cristian Ledesma ran himself into the ground in the middle of the park, winning back the ball for his side and generally being a nuisance for the Inter midfield. It was the kind of performance Mazzarri needs from Zdravko Kuzmanovic or Mateo Kovacic, both of whom were poor.
Out wide, Lazio were better too. Antonio Candreva, in particular, was excellent and though Klose got the plaudits for scoring the winning goal, the German will have known who to thank afterwards. The Roman winger was hard-working, committed and creative. His opponents were not.