You might have missed it as the camera angle was panned down to a close-up on the corner flag in the 79th minute. With Liverpool 3-0 ahead against Barcelona in their Champions League semifinal second leg but tied 3-3 on aggregate, the announcers were taking a breath ahead of what seemed like a run-of-the-mill corner kick and even Anfield itself seemed quiet.

An extra ball rolled over to a scampering ball boy; Xherdan Shaqiri shuffled toward the corner flag and Trent Alexander-Arnold measured his steps away from the ball. Then, while the Barcelona players were still setting up their marking assignments, Alexander-Arnold suddenly cut his set-up short, scampered back to the ball and bent in a low cross along the ground to Divock Origi, who was standing unmarked in the 6-yard box.

All commentator Martin Tyler could spit out was "QUICKLY TAKEN" before Origi's shot looped in at the first post. That made the score Liverpool 4-0 Barcelona -- the comeback after a 3-0 first-leg defeat was complete, and a couple of weeks later Jurgen Klopp's team would lift the European Cup in Madrid.

Given what Liverpool would go on to do, Origi's second goal against Barcelona was probably the most important goal of the season. And it was also the most fitting.

Back in September, Liverpool hired a throw-in coach. Yes, a throw-in coach. It was an easy target for bad jokes but nearly 12 months on, it looks like a clear indication of the club's new dedication to dead balls. According to postgame reports, everyone at the club -- all the way down to the ball boys -- were briefed on the potential for a quick corner kick against Barcelona. It wasn't a pre-scripted play, but Liverpool were able to capitalise in that specific moment because everyone involved knew there was a chance something similar would arise.

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Thanks to that newfound focus, Liverpool led all teams in Europe's "Big Five" leagues with 22 goals from set pieces last season in domestic play; no one else had more than 17. Take a couple of those away and there's no title race in England and perhaps no sixth European title, either. But Klopp & Co. aren't the only dead-ball dynamos to experience success last season.

Their opponents in the Champions League final, Tottenham, were joint-fifth (16), as were their semifinal opponents, Barcelona, and the Serie A champions, Juventus. Germany's title winners, Bayern Munich, were just one back with 15 (in four fewer games), while France's finest, Paris Saint-Germain, snuck into the top 25 with 13. And guess who led the Champions League in set piece goals? The surprise semifinalists Ajax, with eight.

Despite the attacking talent and beautiful, complex interplay these teams are all capable of from open play, they each needed dead-balls to score as many goals as they did. Set pieces, then, are as important as they ever have been.

Back in 2014-15, FC Midtjylland, a small club located on the Jutland peninsula, won its first-ever Danish league title. The club is owned by Matthew Benham, a former hedge fund manager and sports bettor who also owns Brentford in the English Championship. Under Benham's ownership, Midtjylland have become the closest thing in European soccer to a professional baseball team: unafraid of unconventional behaviour, looking for inefficiencies wherever they can find them. During that championship campaign, they scored 25 set piece goals while no one else in the 12-team league broke 11 and just three others reached double-digits.

One of the reasons why some coaches, players and analysts bristle at the idea of spending more practice time on set pieces is that practice time is finite. The more time you spend on set pieces, the less time you're spending on possession; wouldn't the improvement in dead-balls just be cancelled out in the decline in production from open play?

Eventually, everyone else in Denmark started to copy Midtjylland. In the 2017-18 season, they led the league with 25 set piece goals again and they won the league again, too. Except, this time, two other teams broke 20 set piece goals, and eight others broke into double-digits.

"It was almost an unintentional economics experiment," Ted Knutson, who used to work for Midtjylland, told ESPN.

The league had expanded to 14 teams, but the number of set piece goals per game had increased from 0.55 in 2014-15 to 0.75 in 2017-18. On top of that, the number of goals also increased, from 2.41 per game to 2.91. Everyone got better at set pieces and everyone scored more goals.

"It pointed to a huge under-exploited tactical wrinkle in the game that could help teams score enough goals to win a title," Knutson said. "And it's repeatable across the entire sport. That's a pretty big deal."

Knutson now runs Statsbomb, an analytics consultancy with clients across the world. They also teach a course on set piece design.

"Right now, the average team scores between 0.30 to 0.35 goals a game from set pieces," he said. "The best teams can bump this up to 0.75 to 0.80. That type of leap in production takes an average Premier League forward and moves them into the realm of Neymar, except without the transfer fee or the massive cost in wages."

Liverpool averaged 0.58 set piece goals per game last season, so Knutson believes that not even the best team is executing on set pieces as best as it can. But his comparison still works: Only seven Premier League players (Sergio Aguero, Pierre-Emerick Aubameyang, Sadio Mane, Harry Kane, Gabriel Jesus, Mohamed Salah and Jamie Vardy) averaged more than 0.58 goals per 90 minutes last season.

Given everything that could go wrong, every open-play goal is a minor miracle. In order to develop an efficient and productive open-play attack, there has to be an innate understanding between players who must move in sync with each other and then execute a succession of high-level skills at a fast pace. They're never replicating an exact pattern of movement or passing -- every goal is as unique as a snowflake -- but rather constantly interpreting a set of pre-practiced principles. That takes a lot of time to develop. But with set pieces, teams can literally import the exact routines they practice directly onto the field.

The 2018 World Cup was further proof that dead-ball training can provide immediate dividends. National teams simply don't spend enough time together to develop the necessary open-play cohesion. (It's not a coincidence that perhaps the two best international sides of the past 10 years, Spain and Germany, included an outsize number of players from Barcelona and Bayern Munich.) But they can develop their set piece proficiency.

In Russia last summer, there were 70 set piece goals, eight more than the previous record set in 1998. Gareth Southgate studied the plays of both NBA and NFL teams before the tournament, and then England scored nine set piece goals, breaking the record Portugal set back in 1966.

However, despite both England and Liverpool's success with set plays, the best team in the U.K. is still lagging behind. Manchester City's 12 set piece goals were tied for eighth most in the Premier League last season. Pep Guardiola's side had the best goal differential of any team in Europe in 2018-19. Could there still be room for improvement?

"Pep is a genius, but Man City can definitely get better at executing in that one phase of the game," Knutson said. "I'm not sure it will be good for the Premier League as a whole if they do though."