It’s all about fullbacks.

A year ago, Pep Guardiola and Manchester City spent more than £118 million on three players at what, traditionally, has been viewed as a tertiary position. By definition, fullbacks defend the least dangerous part of the final third, and they attack the least dangerous part of the attacking third. The most expensive of City’s trio was Monaco’s Benjamin Mendy, who arrived for £48.88 million. He went down with a knee injury six games into the season, Guardiola replaced him with Fabian Delph — up to that point an unspectacular journeyman midfielder — and the club cantered to a record-shattering Premier League title.

Maybe … anyone could play fullback? Not so fast. Mendy has played every minute for City so far this season, and he’s tied for the league lead in assists with Watford’s José Holebas, another fullback! Here’s Opta’s Duncan Alexander, writing for the BBC:

Mendy has produced more open-play crosses than any other player (27, followed by fellow full-backs Trent Alexander-Arnold, Kieran Trippier and Cesar Azpilicueta), while new Scotland captain [Andy] Robertson has created as many chances this season as Mesut Ozil and Paul Pogba combined.

On top of that, according to Alexander, defenders have accounted for 37 percent of Premier League assists this season. Last campaign, they created just 21 percent of the goals. Four games into this season, it’s the fullback’s world; we’re all just watching them whip in an overwhelming number of crosses. And don’t expect that to change this Saturday, when first-place Liverpool head to Wembley to take on fifth-place Tottenham.

According to our Watchability Rankings, this is by far the most watchable Premier League game of the weekend. And it’s the only game in Europe to feature two teams (Liverpool no. 4, Tottenham no. 15) in our top 15. (It’s not the most watchable, though: Real Madrid [no. 3] and Athletic Bilbao [no. 16] have a higher combined watchability score.) That Spurs-Reds is the game of the weekend should not come as a surprise: Mohamed Salah! Harry Kane! Jürgen Klopp! Mauricio Pochettino! Both teams have finished in the top four in the previous two seasons. It’s two of the most proactive and aggressive defenses in the league, and two sides that try to cram as many creative players into their midfields as possible. Last season’s matchups saw nine goals over two matches — including two of the goals of the year, from Salah and Victor Wanyama.

But despite all the attacking talent and the midfield muscle, and even though Liverpool and Tottenham spend less time in their own defensive third than any teams in the league other than Manchester City, the fullbacks seem most likely to play a decisive role in Saturday’s game.

As Ringer contributor James Yorke wrote for StatsBomb — and Grace Robertson reiterated in her preview of the match on Thursday — Tottenham’s defense has not been effective since the final 10 or so games of last season. Over that stretch and up to now, they’ve given up roughly as many goals as they’ve conceded. The culprit? England’s unlikeliest of World Cup heroes, the Bury Beckham, Kieran Trippier. Since April, an overwhelming proportion of the key passes Tottenham have allowed — i.e., passes that have directly led to a shot — came from the right-back zone. As Yorke wrote, “Tottenham’s opponents have received in excess of … 100 more passes in the right back zone (up to 40 yards from goal) than on the other side of the pitch during the same recent period.”

Liverpool’s right-sided attacker, Sadio Mané, has come out of the gates on fire this year, tied with Fulham’s Aleksandar Mitrovic atop the league’s goal-scoring leaderboard with four. But he’s yet to record an assist, and he’s fourth on the team in key passes per 90 minutes and fifth in total expected assists (the number of goals, on average, we’d expect his teammates to score from his key passes). On the other side of the field, Salah leads the league in expected assists (and expected goals — yes, he’s arguably been better than he was last year), but second is Liverpool’s left back, Andy Robertson. If anyone is going to exploit Tottenham’s biggest weakness, it’s the 24-year-old Scottish captain.

Of course, it’s not as if Trippier’s just a traffic cone; part of the reasons his side of the field is so open is because he’s so involved in the team’s attack. The 27-year-old has essentially just swapped his England shirt for a Tottenham top, but he’s playing the same way: Trippier led his national team in chances created per 90 minutes, and now he’s doing it for his club. Like this summer, some of that comes from his status as one of the team’s designated corner-kick takers, but the push-and-pull between two players who cost just a combined €14 million should be one of the defining features of a game between two of the top 10 teams in the world. On the opposite side, Liverpool’s Trent Alexander-Arnold has just two key passes so far and is tied for the league lead in most inaccurate crosses, while Ben Davies takes up much more conservative positions than any of the other three fullbacks, but he’s also leading Tottenham in expected assists this year. All four fullbacks are active; Saturday’s match might come down to which one is most effective.

For Tottenham, the game is an opportunity to show that the team is back on track with a solid performance against a high-flying side they really got the better against in both games last year. And for Liverpool, it’s a chance to prove that their dominant start to the year won’t dissipate against better competition, which is especially important as they begin the potential death march that is the next month. In addition to Tottenham (and Southampton), they play PSG, Napoli, Chelsea twice, and Manchester City over the next 25 days.

Anything and anyone can win a single game, especially with the talent across Klopp’s and Pochettino’s rosters. Raise your hand if you had “Wanyama thunderbastard” on your Liverpool-Tottenham bingo cards last season. But while Christian Eriksen pings perfect long balls and Naby Keïta redefines the concept of “midfielder” in real time, don’t forget about the guys bombing up and down the sidelines.