The fourth matchday of the Champions League group stage kicked off on Tuesday with eight matches, but not as many goals as we've been used to -- 21 in total with Barcelona and Chelsea held scoreless. Here's what to know and see: 

Tuesday's Champions League scores

Manchester United 2, Benfica 0
Atletico Madrid 1, Qarabag 1
Bayern Munich 2, Celtic 1
Barcelona 0, Olympiacos 0
PSG 5, Anderlecht 0
Sporting Lisbon 1, Juventus 1
Roma 3, Chelsea 0
CSKA Moscow 2, Basel 1

Chelsea thrashed on the road

It was a bad night for the Blues. The London club got rocked by Roma at the Stadio Olimpico, with Stephan El Shaarawy scoring twice in the first half. The Blues won the possession battle and put six shots on frame, but Roma goalkeeper Alisson was in fine form, reacting well to hold Eden Hazard, Alvaro Morata and the Blues to their first scoreless game in Sept. 30 (a 1-0 loss to Manchester City).

Atletico in trouble

Don't look now, but Champions League darkhorse Atletico Madrid may not make it out of the group stage. Diego Simeone's team is going through a tough spell and is now four points back of second-place Chelsea with two games to go. They obviously still have a chance to go through, but the problem is the the tough schedule ahead. The team has to face Roma and Chelsea to finish out the stage and didn't take advantage of its opportunities against lowly Qarabag, drawing 0-0 on matchday three and 1-1 on Tuesday. Atletico probably figured it had at least four points but probably six in the bag playing Qarabag. Instead, they leave with only two points in two meetings against the Azerbaijan club.

United fortunate again 

Manchester United may not always play the most attractive style, but they are getting results. And they did that again thanks to a little luck. After a blunder from Mile Svilar helped United beat Benfica on the last matchday, another error helped them win on Tuesday against the Portuguese side.

Relive match commentary:

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