The tie between Sevilla and Leicester isn't the most glamorous in Champions League history -- pre-round-of-16 odds had neither club among top nine favoured to win the trophy -- but that is precisely what makes this meeting so fascinating: Sevilla and Leicester are two of European football's overachievers, albeit in completely different ways.

The Champions League has become depressingly repetitive in recent years -- this round has seen Bayern Munich and Arsenal and Paris Saint-Germain and Barcelona meet yet again -- so a clash between two sides that have never faced one another offers genuine intrigue. The fact Sevilla and Leicester are considered such outsiders, despite the fact they are the Europa League and Premier League champions respectively, partly explains how routine the tournament has become.

Regardless of last season, these two sides have been among the most interesting sides tactically over the past 18 months. Sevilla were a very fine, well-organised team under Unai Emery but, after his decision to join PSG last summer, the appointment of Jorge Sampaoli meant a change to a more attractive, high-tempo, attack-minded approach.

Sampaoli, who made Universidad de Chile into South America's most attractive club team and Chile into the continent's most attractive international outfit, is working his magic but, more crucially, he also has a track record of success, having won the Copa Sudamericana in 2011 and the Copa America four years later.

He's unlikely to win a major honour this season, which might seem something of a disappointment for three-time Europa League winners Sevilla, but there has already been clear progress; Sevilla have mounted a decent title challenge and have reached the final stages of Europe's major club competition.

Sampaoli is a great admirer of Marcelo Bielsa and replicates the Argentinean manager's high-intensity, heavy-pressing system, but does so with a more nuance and intelligence. He's not such a committed ideologue; he appreciates the nuances of his individual attackers and his Sevilla side is also tactically flexible.

Keeping up with Sampaoli's formations is almost impossible. For example, he often switches from a three-man to a four-man defence, usually depending upon how many forwards the opposition is playing.

Further forward, there's a rotating band of speedy, technical, elusive forwards. Wissam Ben Yedder, Luciano Vietto, Franco Vazquez and Vitolo have all starred at various points this season and Samir Nasri has enjoyed perhaps the best campaign of his career, enthusiastically adapting to his manager's demands.

Stevan Jovetic, meanwhile, has been rescued from an unhappy spell at Inter and contributed crucial goals already. Sampaoli deserves praise not merely for getting these players performing, but keeping them all happy.

Perhaps his key player, though, is Steven N'Zonzi, the tall, commanding, holding midfielder who guards the Sevilla defence, breaks up play and distributes the ball intelligently. In such a young, energetic squad he feels like something of an elder statesman, even if he's only 28, and his discipline might be vital against a Leicester side based primarily around counter-attacking.

Indeed, while Leicester are playing abysmally in the Premier League at present, Sevilla might be the type of opponents they enjoy facing. The Spanish club play a high defensive line, they push their full-backs forward and commit plenty of men into attack. And that, at least on paper, is a recipe for Leicester's counter-attacking style.

There's a chance Leicester could return to the form they showed last season. So often, teams struggle in the league and are under pressure with relegation looming, yet perform miraculously in cup competitions. Jamie Vardy and Riyad Mahrez, so underwhelming this season, could spring back into top form.

Leicester's first task, though, is to defend solidly. Last season they went on an astonishing run of 1-0 victories during the title run-in, with full-backs tucked in and the midfield sat deep, as Wes Morgan and Robert Huth remained in the penalty box and constantly headed away crosses.

This season, by contrast, their defensive structure has been extremely poor. Claudio Ranieri's men will need to defend deep to cope with Sevilla's nimble attackers and that means the Leicester midfielders and full-backs must protect the centre-backs reliably. From there, Mahrez is the key player.

It's still difficult to work out whether Vardy is a one-season-wonder or simply not getting the service this season, but Mahrez has pretensions to be considered one of the best attacking midfielders in Europe. On this stage, he'll be particularly determined to impress, possibly to earn a move for next season. In fact, Sevilla might be a favourable destination.

Mahrez is a true all-rounder: A mazy dribbler, a clever passer, a ruthless finisher and, for all Sevilla's attacking quality, he will be the most talented player on display over the two legs. Champions League ties are so often won by counter-attackers and Mahrez seems the most likely to dominate.

This is, therefore, a tremendous clash of styles. It's a high line against a deep defence, attacking combination play against individualistic counter-attacking, an in-form side against a team performing worse than anyone could have anticipated. A fixture that won't be repeated again any time soon, it has the makings to be truly wonderful.

The best thing, though, is that one of these sides will progress to the quarterfinals, meaning we'll have something of an outsider in the final eight. It will be fascinating to see how a possession side would respond to Sevilla's press, or attempt to negate Leicester's counter-attacking.

Sevilla and Leicester aren't the best sides in this season's Champions League but they boast the most distinct, unusual styles. In a tournament that has become far too samey in recent years, that should be celebrated.