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After Liverpool and Bayer Leverkusen secured a fairly easy passageway to the Europa League round of 16, the list of contenders vying for the continent's second biggest club prize will only get longer thanks to the Champions League third place teams who drop down to the competition.

The pair are still the favorites to lift the trophy next spring and are arguably the most notable sides to advance to the knockouts as group stage winners. After an entertaining group stage in both the Champions League and the Europa League, a few high-profile matchups could be in the cards for the knockout round playoffs, where Europa League group stage runners-up face off with the Champions League third-place sides. The winners in the playoffs will then meet up with the Europa League group winners, which could mean tough competition as soon as the round of 16 for the likes of Liverpool and Leverkusen.

Here's a look at the clubs to keep an eye on from the group winners, runners-up and UCL dropdowns:

Group winners to watch

Bayer Leverkusen: Alongside Slavia Prague, Leverkusen are the only side to leave the Europa League group stages with a perfect six wins out of six and are flying high with a four point lead atop the Bundesliga. Xabi Alonso's side enjoyed a European campaign that was as smooth as any, leaving them in the top three among Europa League contenders in just about all advanced statistical categories, including goals for and goals against. That said, their wins came against unmatched opposition -- they played Qarabag, Molde and Hacken in the group stage, so the task for Alonso and company will be to prove that they can dominate against top-tier opposition, also.

Liverpool: Like Leverkusen, Liverpool also rank in the top three in those tactical categories, which is impressive considering Jurgen Klopp opted for some rotation throughout the group stage. The Reds did hit some roadblocks on the way to their first place finish, though -- they lost 3-2 at Toulouse on a day where they won possession and had more shots but were not particularly clinical in front of goal. The question for Klopp will be whether or not his depth options can go toe-to-toe with more competitive sides or if he will need to rely on his top stars in the knockouts -- and how easy that will be to manage during a run for the Premier League title.

Runner-up that can win it all

AS Roma: This season has been far from perfect, but last season's Europa Conference League winners seem to be turning things around and will be one of the teams the Champions League contingent will want to avoid. As is the case with Jose Mourinho teams, the defense has been the key to Roma's success in Europa League -- they let in just four goals in six games, a feat only bettered by Leverksuen. Inconsistency in attack is something they will have to work on for a deep run in the competition, but Romelu Lukaku will serve as a great leader up top after scoring four goals in the group stage.

UCL third-place teams best positioned to win it all

AC Milan: It has been an up-and-down season for Milan, but they picked up two wins in a very competitive Champions League group and sit third place in the Serie A table so prospects remain high for Stefano Pioli's side. The offensive trio of Rafael Leao, Olivier Girod, and Christian Pulisic mean the Italian team has plenty of potential to make a deep run -- they ranked fifth in the Champions League for chances. For them, the task will be living up to the hype since they ranked 30th out of 32 for goals scored during that campaign.

Galatasaray: The Turkish champions have a star-studded lineup that includes Mauro Icardi and Wilfried Zaha and a notable ability to score after notching 10 goals during the Champions League group stage. They also have an above-average ability to let in goals after conceding 13 times during the group stage, so they are poised to entertain even if they cannot always win. Considering they were up against talented sides like Bayern Munich and Copenhagen in the Champions League, they might fare better in the second-tier Europa League.