One of the biggest transfers from the January window gone by was Liverpool's acquisition of Luis Diaz from Porto.
The Colombian international arrived at Anfield in a deal potentially worth up to €60 million. Diaz will bolster Jurgen Klopp's attacking options in all competitions.
Liverpool crossed paths with Diaz and Porto in Group B of the Champions League this season. The Reds won both games on their route to top the group.
The 25-year-old impressed in those fixtures despite being on the losing end in both games. Most notably Liverpool were dominant in a 5-1 win in September.
It's not the first time Klopp has signed a Champions League opponent for Liverpool. Since the German took charge in 2015, there are several other examples.
Liverpool's Champions League Scouting
The first case is the signing of Alisson Becker from Roma. Since his arrival in the summer of 2018, he's been a mainstay as Liverpool's number one.
Liverpool faced AS Roma in the semi-final of the 2017/2018 competition and the Italian club had been a bit of a fortress defensively in home games at Stadio Olimpico.
With a backline of the likes of Federico Fazio, Kostas Manloas and Juan - they hadn't conceded a goal at home in Champions League competition that season.
That was until Liverpool made the trip to the Italian capital. Despite winning 4-2, Roma ended up going out 7-6 on aggregate after the Reds put five past them at Anfield.
Alisson conceded seven goals over two legs but was signed two months later. His performances in Europe put his name on the map as he earned 22 clean sheets domestically.
ON THIS DAY: In 2018. Liverpool confirmed the signing of Alisson Becker from AS Roma for €75m.
👕 51 games
🧤 27 clean sheets
🏆 Champions League
🥇 Premier League Golden Glove
An incredible debut season. pic.twitter.com/dK1kFWbUXf— Squawka (@Squawka) July 18, 2019
The following season was to be a crowning moment for Liverpool in the Champions League. They would go on to win it outright in a 2-0 victory over Tottenham in the final.
During the 2018/2019 campaign, they came across Bayern Munich in the Round of 16. One of the standouts for the German champions at the time was Thiago Alcantara.
The Spaniard earned the Bundesliga/Supercup/DFB Pokal treble that season and played a pivotal role on their route to winning the competition the following year.
Thiago was brought to Liverpool a year on from their Champions League knockout stage encounter. He impressed in another treble winning season for Bayern that year.
The 2019/2020 Champions League campaign saw Liverpool drawn with Napoli, Genk and Red Bull Salzburg. Despite running them close, Napoli ended up runners-up.
The Reds topped the group and in doing so, overcame the challenge of a young, talented Salzburg team on two occasions. Erling Haaland led the line for the Austrians.
Takumi Minamino scored two group goals in that campaign including one at Anfield in an eventful second round encounter which saw Liverpool win 4-3.
The return leg in Austria was less eventful, however Minamino put in a spirited performance. Jurgen Klopp didn't wait too long to secure his services.
Three weeks after that game, the Japanese international agreed a deal to come to Merseyside. He had obviously left a lasting impression after their two Group E games.
🗣 Virgil van Dijk on Takumi Minamino:
"I think Taki has been very good.
"After lockdown, he has been the Taki that we all saw when we played against him at Salzburg.
"He is very, very energetic and he is a fantastic player." pic.twitter.com/UluZZ4BOoG— GOAL (@goal) August 30, 2020
With Liverpool upset by Atlético Madrid in the Round of 16 that year, the following season brought more hope that they could go all the way in Europe.
Despite the ongoing pandemic, the 2020/2021 Champions League continued behind closed doors and Liverpool would go on to meet RB Leipzig in the Round of 16.
Both teams were affected by Covid-19 restrictions but most notably Leipzig. They had to host their 'home' game in Budapest due to German regulations at the time.
Two comfortable 2-0 wins saw Liverpool through to the next round of the competition. Leipzig weren't close to repeating their semi-final adventure of a year prior.
One of the stars of that run was defender Ibrahima Konaté. He played nine times in Europe that year, scoring twice, but fell down the pecking order due to injuries.
He was an unused substitute for the two Liverpool legs but it's likely Klopp and his scouts did plenty of preparation on Leipzig's defensive setup before their meeting in Europe.
Something must have stood out for him watching Konaté, as three months after their Champions League meeting he was unveiled as a Liverpool player.
It's a telling bit of history. Teams do plenty of research on their opponents for big games such as those in Europe, but Klopp seems to treat is as a scouting mission.
Season after season, he's brought in players that have impressed against Liverpool. Luis Diaz is another example of a long tradition of signing Champions League opponents.
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