The Champions League round of 16 got underway on Tuesday with Manchester United hosting Paris Saint-Germain and Roma welcoming Porto to the Italian capital. In England, Kylian Mbappe and Presnel Kimpembe found the back of the net for the Parisians in a commanding 2-0 win that saw Paul Pogba sent off on a red card. Meanwhile, Roma secured a 2-1 victory, though the Portuguese side finds itself in a solid spot with what could be a vital away goal from Adrian Lopez. With that said, let's dive into what you need to know from these two knockout stage matches. 

No Neymar and Cavani, no problem for PSG

Manchester United entered this match in fine form under Ole Gunnar Solskjaer and PSG was dealing with the injury absenses of Neymar and Edinson Cavani. You would think that would have evened the scales a bit for United. Far from it. The quality of play out of PSG, even without two of its key stars, was evident. Marco Verratti was a rock in the middle of the field and the team dictated the pace with its speed, leaving United in the dust. 

Kimpembe scored the opener, Angel Di Maria was able to terrorize his former team with a brilliant through ball to Mbappe who made it 2-0 on the hour mark. Take a look:

You could hardly tell this was a PSG team playing without two of its better players. PSG had 12 shots, five on frame and Gianluigi Buffon only had to make one save on the night. 

Just when it seemed like the injuries could doom PSG, now its practically a lock to move on to the last eight of the Champions League.

Pogba red card hurts United comeback bid

With a 2-0 deficit and Pogba missing the second leg after picking up a red card, it's incredibly hard to envision how United can get back into this tie. Pogba has been unbelievable under Solskjaer and playing with such confidence, and United doesn't have a natural replacement who can dominate the ball, set up teammates and also put the ball away himself. With him, they would have still had a chance. Without him, it feels like mission impossible. 

If United has any hope of making this interesting, it's going to learn how to defend. On the opener from Kimpembe, Nemanja Matic fell asleep when defending the corner kick. Look at the goal and how he just stops for no reason at all:

Not how to get it done. 

Porto still alive with away goal at Roma

Nicolo Zaniolo scored twice in seven second-half minutes to give Roma a 2-1 lead, but it was Lopez's goal for Porto 11 minutes from time that leaves this one up in the air. A 2-0 lead for Roma would have been commanding, but now just a 1-0 win at home for the Portuguese side will see them through. 

While Roma will hate that it conceded, they'll still feel confident entering the second leg knowing that scoring once in the second leg will force Porto to try and score two. It's nearly an even tie after the first one. In its last three away games, Roma has allowed 10 total goals. 

Roma's Zaniolo could be next big thing from Italy

Nineteen-year-old striker Nicolo Zaniolo looks like the real deal for Roma. The highly-rated young midfielder, who joined last summer from Inter Milan, scored twice to bring his season tally to five. With Eden Dzeko struggling and Stephan El Shaarawy leading the team with eight goals, this team has had to rely on other players to deliver. Considering that defender Aleksandar Kolarov is the team's second-leading scorer with eight, the opportunities from others outside the strikers really need to be converted as they aim to find their scoring touch.

And no goal shows Zaniolo's quality to put the ball away than his first. Look at the quick, low shot across his body to the far post. Brilliant. 

Wednesday's UCL fixtures

Two of the eight first leg matches are in the books. On Wednesday, Tottenham hosts Borussia Dortmund and Ajax welcomes Real Madrid to Netherlands. Both matches get underway at 3 p.m. ET and can be streamed via fuboTV (Try for free).

CBS Sports was with you the entire way during Tuesday's Champions League action. If you are unable to view the live updates below, please click here.

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