Liverpool, Manchester City, Manchester United and Chelsea are back in Champions League action this week.
All four English clubs play the return legs against the sides they faced in the third round of group matches earlier this month, with Chelsea and United first up on Tuesday against Rennes and Istanbul Basaksehir respectively.
On Wednesday, Liverpool take on Atalanta at Anfield, while City travel to play Olympiacos.
Here, the PA news agency takes a closer look at the opposition clubs.
Rennes: Julien Stephan was part of Rennes' coaching staff before stepping up to replace Sabri Lamouchi as boss in December 2018. They won the Coupe de France that season and third place in Ligue 1 last term has taken them into this, their first ever Champions League campaign.
Istanbul Basaksehir: Okan Buruk became manager of Basaksehir in the summer of 2019 and in the season that followed led them to their first ever league title. The former Turkey midfielder finished his playing career with the club, having spent much of it with Galatasaray and also had a spell with Inter.
Olympiacos: Former Portugal international Pedro Martins took charge of a club outside his homeland for the first time when he was appointed as Olympiacos coach in 2018. Under him the Greek outfit won a domestic double last season and got to the last 16 of the Europa League – eliminating Arsenal in the last 32, then losing to Wolves – following a Champions League group-stage exit.
Atalanta: After a brief spell as Inter Milan boss in 2011, Gian Piero Gasperini managed Palermo and then Genoa before becoming Atalanta coach in 2016. He subsequently guided them into the Champions League in 2019 with a third-placed Serie A finish and their debut campaign saw them reach the last 16.
Rennes: Rennes' Champions League bow this term comes after Europa League campaigns in each of the last two seasons – getting to the last 16 in 2018-19 was their best run in the competition.
Istanbul Basaksehir: The club made their European debut in 2015-16 in the Europa League qualifying rounds and got to the last 16 of the competition last term. This is their first season appearing in the Champions League group stage.
Olympiacos: The best performance by Olympiacos in Europe was reaching the quarter-finals of this competition in 1998-99, where they were knocked out by Juventus.
Atalanta: The Italian club reached the Cup Winners' Cup semi-finals in 1987-88 and the UEFA Cup quarter-finals in 1990-91. That was their last continental campaign until they played in the Europa League in 2017-18, before making their Champions League bow two years later.
Rennes: Rennes have lost their last three games in all competitions. Since being beaten 3-0 at Stamford Bridge they went down by the same score at Paris St Germain and were beaten 1-0 at home by Bordeaux on Friday. Their first two Group E matches ended in a 1-1 home draw with Krasnodar and a 1-0 loss at Sevilla. They have slipped from third to seventh in Ligue 1 after three defeats from their first 11 matches.
Istanbul Basaksehir: Since registering their first Champions League win by beating United 2-1 in Group H, Basaksehir have beaten Turkish League rivals Genclerbirligi, but lost 3-2 at Besiktas on Saturday and are sixth in their domestic table. In their opening two Champions League group games they
suffered two 2-0 defeats, at RB Leipzig and then at home to PSG.
Olympiacos: Olympiacos are third in Group C after their 3-0 defeat to City at the Etihad Stadium had followed a 1-0 home win against Marseille and a 2-0 defeat in Porto. Their 1-0 defeat of Panathinaikos on Saturday was their fourth straight win in the Greek top flight and they are currently top of the table on goal difference.
Atalanta: Before their 5-0 thrashing by Liverpool in Bergamo, Gasperini's men had opened their Group D matches by beating Midtjylland 4-0 in Denmark and drawing 2-2 at home against Ajax. They are third in their pool and seventh in Serie A after respective 1-1 and 0-0 draws at home against Inter Milan and Spezia.
All eight clubs are facing their respective rivals for only the second occasion having met for the first time in the reverse fixtures earlier this month.