When Napoli burst into the knockout rounds by overpowering Manchester City, I joked on Twitter that it would only take a day for star Edinson Cavani to be "linked" with a Premier League team by the voracious English press. I was wrong: it took less than an hour for a "report" to surface that the Uruguayan hitman was coveted by everyone from Arsenal to East Fife.

There's a reason why Cavani is so desired, and Chelsea is about to find it out at exactly the wrong time. The Londoners are mired in a bad slump, are feuding internally, and have a manager who has been forced to issue defiant statements about his job security every single day. For once, the mighty Blues are the underdogs, and it is fair to say their season hinges on this night at the San Paolo Stadium.

Napoli will host Chelsea in the marquee Champions League game of the day as the knockout stage rolls on. Coverage begins on FOX Soccer at 2 p.m. ET and will be preceded at noon by CSKA Moscow versus Real Madrid. (Every Champions League game is on the FOX family of networks and all the game day action can be followed in real time on FoxSoccer.com and via Twitter @FoxSoccerTrax .)

The Italians, unbeaten in 11 home games in European play at the San Paolo, present a real tactical headache for Chelsea manager Andre Villas-Boas. Moreover, it's not clear the young manager has the tools to address them. There has been significant drift at Chelsea over the past two months, and a side that once styled itself as an attacking dynamo has been forced to cobble together points any way it can.

Some of the blame for the troubles at Chelsea have to fall squarely on Villas-Boas. He has simply looked unable to adjust to changing conditions in-game. New questions about his authority were also raised again this weekend after a grim 1-1 FA Cup draw against Championship side Birmingham after it was leaked that Didier Drogba gave the halftime team talk.

But it also has to be said that some of the key players simply haven't performed up to past standards. Fernando Torres' scoring drought is no longer laughable - it's pitiable. The once-fearsome Spanish striker has been reduced to getting votes of confidence from second division defenders and has the stare of a man trapped in a waking nightmare. John Terry's antics have finally caught up with him, and his on-field play has slipped yet another notch. And Ashley Cole, once the best left-back in England, looks bereft of skill this season.

Villas-Boas is expected to finally drop Torres and is facing fitness doubts on Terry and Frank Lampard. As such, Napoli's front three - Cavani, Marek Hamsik and Ezequiel Lavezzi - should be able to fully exploit Chelsea's key weakness: the lack of pace in the back and their indiscipline in central midfield. Cole has regressed badly, Branislav Ivanovic is clumsy and erratic, and David Luiz has yet to show footballing brains to go along with his raw skills.

Given the way that Napoli's top trio can knock the ball about, Terry's absence might actually be a blessing in disguise. Terry is no longer unable to handle strikers at pace and can no longer hide his need to keep the play in front of him. As a team, Chelsea are deeply vulnerable to balls passed over or around their back line. Further, because they have been unable to hold the ball in the middle of the field, they cannot play at the pace needed to compete at the very top level.

Michael Essien's return to the competition should help stabilize what has been a dreadful midfield, but how well he can move the ball upfield to the classy Juan Mata is an open question. He is the vital link, and as such is certain to be harassed by both Hamsik and Gokhan Inler.

Where Chelsea does have strength is up top, with Daniel Sturridge and the still-impressive Drogba expected to focus on peeling away Napoli's left wing back (possibly Andrea Dossena) to test goalkeeper Morgan De Sanctis. De Sanctis' distribution has been a career problem, and the Napoli `keeper can be forced into making errors if put under pressure. If Mata is able to find space wide to swing the ball in, Chelsea can profit.

Unfortunately, that's happened far less often of late and Chelsea look like a side clinging to life. Chelsea's last win over a quality team came over two months ago, a 2-1 December win over Manchester City. They've triumphed only once in their last six games and looked psychologically shattered by Manchester United's stunning fight back two weeks ago that saw them let a three-goal lead slip.

Villas-Boas has remained stoic, insisting that Chelsea's notoriously impatient owner Roman Abramovich is on board with "the program." But the Russian oligarch's visits to the training ground have increased in frequency over the past two weeks, and vultures are circling. Yet the one thing that may keep Villas-Boas in his job is the need for fiscal prudence. Chelsea apparently spent over $100 million in firing and hiring managers over the past four years, with the hiring of Villas-Boas and the sacking Carlo Ancelotti accounting for close to $45 million of that.

One key man will be watching from the stands. Napoli gaffer Walter Mazzarri shoved Villarreal's Nilmar during the group stages in an ugly touchline incident and is suspended for both legs after UEFA rejected his appeal last week.

The first game of the day pits red-hot Real Madrid against CSKA Moscow on the artificial turf of the Luzhniki Stadium. It shouldn't be close.

Cristiano Ronaldo is in record-breaking form, lifting his goal tally to an astonishing 120 in 123 games for the Spanish giants on the weekend. Ronaldo also leads La Liga with 28 goals and got the first in just seven minutes as Real collected their 18th win in 19 games, a 4-0 drubbing of Santander on Saturday.

Real swept through the group stages with six straight wins and look supremely confident. The only absence for them is Angel Di Maria (leg), and they shouldn't miss him. Xabi Alonso and Mesut Ozil are both expected to have plenty of time and space against a CSKA side with a lot of holes, and Kaka is hardly a shabby replacement for Di Maria.

Real face a CSKA side that looks dramatically different from the one that crept into the knockout round with a killer last day win over Inter Milan at the San Siro. Riven by injuries and suspension, CSKA also sold its most recognizable player, Vagner Love, in the transfer window. The Russians will be missing key men three other key men to injury: goalkeeper Igor Akinfeev, midfielder Keisuke Honda, and winger Mark Gonzalez.

Two players to keep an eye on at CSKA are new signing Pontus Werbloom, tireless at AZ Alkmaar; and Seydou Doumbia, who is struggling with confidence and fitness following an African Nations Cup stint that saw him riding Cote D'Ivoire's bench. Doumbia is considered an up, and comer but how he fares against Real's gritty defense is an open question.

Few expect CSKA to offer more than token resistance, but the field and the weather will play major parts. Moscow is forecast to have temperatures in the teens at kickoff, and the Luzhniki's surface is notoriously slick. Expect that to affect but not derail Madrid.