Liverpool v Napoli: Three key battles

A 1-0 win or victory by at least a two-goal margin will guarantee the Reds' progress to the knockout rounds, but any other result could mean elimination.

It's a high-stakes clash, and here are three key battles that could help determine the outcome of the tie...

Mohamed Salah v Kalidou Koulibaly

Napoli centre-back Kalidou Koulibaly was unveiled as a contender for UEFA's Team of the Year on Monday and it's easy to see why.

The 6'4" colossus played every minute for Senegal at last summer's World Cup and has started all 20 of Napoli's games across all competitions this season.

Quick, tall and powerful, he is the rock at the heart of their defence. An excellent ball-winner on the deck and in the air, he's also composed in possession.

Since the start of last season, no player has completed more than Koulibaly's 3,696 passes (per Whoscored) in Serie A.

Salah's average position against Napoli (left) in October compared with against Bournemouth (right) at the weekend.

But he'll have his work cut out at Anfield against Liverpool's leading scorer, Mohamed Salah, who netted a hat-trick in the 4-0 Premier League win over Bournemouth at the weekend to take his season tally to 12 strikes.

Stationed mainly on the right flank in the first clash in Naples, Salah has typically been the most advanced forward for the Reds in more recent matches.

The average position heatmaps above show how the No.11 has evolved into the point man of Liverpool's attack, and that will bring him into direct competition with Koulibaly.

Naby Keita vs Allan

Allan has played more minutes (1,533) for Carlo Ancelotti's Napoli than all but stalwart centre-back Koulibaly (1,800).

Now in his fourth season at Stadio San Paolo, the 27-year-old defensive midfielder has become the lynchpin of I Partenopei’s pressing game and technical build-up play following Jorginho's departure for Chelsea.

Only AC Milan's Lucas Biglia averages more tackles per game in Serie A than Allan's 3.9, but the Brazilian is also more than adept at bringing the ball up the pitch when in possession. This season, he averages a team-high 1.6 dribbles per game, has a pass completion rate of 89.5 per cent and has chipped in with two assists.

His impact on this Napoli side is clear and counteracting that influence is likely to be one key to Liverpool's success.

Reds boss Jürgen Klopp has a variety of midfield options available but the dynamic Naby Keita has really impressed in the last two matches - putting in a Man of the Match performance in the 3-1 comeback win against Burnley and catching the eye once again in Saturday's 4-0 victory at Bournemouth.

A box-to-box player, he features heavily at both ends of the pitch. Against Burnley, he led the team in blocks and possession regains (10) in defence, had more shots (six) and shots on target (four) than his colleagues in attack, and his passing accuracy of 93.2 per cent was better than anyone else in the match.

The energetic Guinean repeated that latter feat against the Cherries at the weekend and could be the perfect option for a must-win game at Anfield.

Whoever wins this battle could well dictate the tempo of the tie.

Virgil van Dijk v Lorenzo Insigne

Italy forward Lorenzo Insigne has emerged as Napoli's star man under new boss Ancelotti.

Shifted from the left to become a central striker, the 27-year-old has scored 10 goals in 19 matches for his hometown club this season.

Nine of those have come in his now regular position as a second striker, including the injury-time winner in the last meeting with Liverpool.

It's a role which allows Insigne to get more involved in the build-up and he's notched five assists this term, with two coming in his last two outings.

In fact, it is this facet of his game that has come to the fore more recently with the striker having failed to find the net in his last five matches.

It's a relative barren run that Reds centre-back Virgil van Dijk will be hoping to extend on Tuesday.

The diminutive Insigne is unlikely to pose an aerial threat to Liverpool's defensive colossus, but his quick feet, trickery and penchant for a clever lay-off could certainly test the Dutchman on the deck.

However, Van Dijk is far from just a physically imposing centre-back. He is more than comfortable on the ball - leading the team with an average of 77 passes per match - and is an excellent reader of the game.

He has plenty of speed to call upon too, should he need it. The Netherlands international has been clocked as the team's second-fastest player this season at 21.5 mph, just behind injured centre-back partner Joe Gomez at 21.6 mph.

This is a battle to keep an eye on.