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The UEFA Champions League is back this week. Barcelona have already felt the brunt of a superstar performance as Paris Saint-Germain's Kylian Mbappe made is case for being the best player in the world as his hat trick led his side to a 4-1 victory at Camp Nou while RB Leipzig conceded twice to Liverpool in a match relocated from Leipzig to Hungary. Wednesday's action should be just as riveting. You can follow it all on CBS Sports All Access.

The second day of Champions League action features Porto at home to Juventus and Sevilla up against Borussia Dortmund in two enticing matchups with the likes of Cristiano Ronaldo and Erling Haaland on display.

Wednesday's ties have the potential to play out entertaining first and second legs with close first legs expected to lead to gripping conclusions next month, though Tuesday's were expected to as well, before the away sides both accelerated away from their hosts.

Here's a closer look at the second day of round of 16 action.

Gladbach reveal planned Dortmund coaching change

It's never ideal when the story before a big match is all about a coaching change, but that's the situation Dortmund find themselves in ahead of their clash with Sevilla at Estadio Ramon Sanchez Pizjuan. After firing manager Lucien Favre, Dortmund have had a tough start to life under interim boss Edin Terzic with four wins three losses and two draws across all competitions in 2021.

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It's not surprising that Dortmund are planning for life after Terzic, however, BVB appeared unprepared for Bundesliga rivals Borussia Monchengladbach to announce that their head coach Marco Rose has agreed to join Dortmund this summer. But that's what they did on Tuesday.

It has been radio silence from Dortmund since fellow Champions League representatives Gladbach's declaration and it is hardly ideal preparation for a game that was already going to be quite tough with the potential to unsettle the players and Terzic.

Sevilla are one of Europe's form sides at present with nine consecutive wins across all competitions and seven clean sheets with 18 goals scored for just one conceded while Dortmund are struggling for form with two wins from their last seven and one of those required extra time. And they've added some attacking punch since last they appeared in the Champions League as well. During the January transfer window they acquired Papu Gomez from fellow Champions League competitor Atalanta, the kind of creative attacking spark that very well could be the missing piece for a disciplined Sevilla side.

The German attack spearheaded by Haaland against the Spanish defense marshalled by the in-demand Jules Kounde will be one of a number of intriguing battles to keep an eye on in this one while a fatigued USMNT talent Gio Reyna could play some part for the visitors. Despite being a regular for Dortmund the teenager has now gone two months since his last goal on December 12th and even longer since his last assist on November 28th.

Off-color former winners

Porto's meeting with Juventus at Estadio Do Dragao pits a pair of two-time Champions League winners against each other with the Portuguese the most recently title back in 2004.

However, the two teams are not in the best of form at present and find themselves in the unfamiliar position of not being top of their domestic leagues with Porto 10 points off the pace set by Sporting CP and Juventus eight adrift in fourth but with a game in hand to close the gap on new leaders Inter Milan.

This fixture sees Cristiano Ronaldo return to his native Portugal, which is always an event, but neither side has won in their last two matches across all competitions with the hosts on a run of four consecutive draws.

There will be plenty of star power on display with Alvaro Morata one of four players on six goals so far this edition, as is Dortmund's Haaland, and Ronaldo is not far behind them on four.

Both sides will feel that they could have been handed tougher draws and the Italians will look to capitalize on the advantage of being at home for the second leg.

This one will also be of interest to USMNT fans with Weston McKennie likely to play a significant role for Juventus as his development continues after winning his first silverware with the Supercoppa Italia earlier this year. McKennie has benefitted immensely by trading the chaotic environs of Schalke in Germany last season for elite teammates in Turin now. He's scoring at double the rate, going from 0.13 goals per 90 minutes to 0.27, averaging 0.18 assists per 90 after not logging a single one last season. With attackers like Ronaldo and Alvaro Morata in front of him and defenders like Leonardo Bonucci and Matthijs de Ligt behind him, the young American has truly blossomed into an all action midfielder at the top of the European game.