The UEFA Champions League resumes tomorrow night as the fourth matchday of the group stage gets underway, and there are several teams that could clinch a place in the round of 16 if results go their way this week. It should be no surprise that the top three teams in Champions League statistics in regards to goals scored are all in that bunch, in Barcelona (9), Real Madrid (8), and Chelsea (8).

At the same time, there are some teams in potentially perilous positions at the halfway point of the group stage, and they go into this week needing a win and nothing less to improve their hopes of reaching the first knockout round.

Tuesday

Groups E-H take the stage tonight, and Chelsea, Arsenal, AC Milan, and Barcelona could all qualify for the last 16 with victories.

In Group E, Chelsea lead the group with seven points, with Bayer Leverkusen not far behind on six, Valencia struggling on two, and Genk, as expected, bringing up the rear, with only a single point to their name after three matches.

Valencia host Bayer Leverkusen knowing that nothing less than a win will fully maintain their hopes of reaching the round of 16 for the second straight year. If they can only manage a draw, Chelsea will secure qualification with a win at Genk, and after their 5-0 pasting of the Belgian champions a fortnight ago and how fired up they likely will be after letting in five at home against Arsenal on Saturday, you have to expect them to do their part. And if Leverkusen can go into the Mestalla and notch their third consecutive group win, they’ll assure themselves of a place in the round of 16, and will do the same for the Blues if they do as expected and win in Belgium.

In Group F, Arsenal, who lead the group with seven points following their dramatic 1-0 win at Marseille, will qualify if they top Marseille at home and Borussia Dortmund pick up a necessary three points at home against Olympiakos. Arsenal striker Robin van Persie is in unbelievable form at the moment, with five goals in his last two matches and seven in his last four, and he’ll be key to Arsenal getting the three points they need to move on.

If results in Group F go as they should, that will still leave Marseille, who are second with six points, in a favorable position to advance, considering that they host Olympiakos in the next round before finishing up with a trip to Dortmund. Dortmund have one of the best defensive records in the attack-friendly Bundesliga, but they have one of the worst in the Champions League, with seven goals shipped in three matches. Still, even though they’re four points back of Marseille, they’re still not out of the qualification equation, with two home games in their final three matches and a team that’s fully capable of turning it on at any moment.

In Group G, everyone still has a chance to qualify for the round of 16, but it’s APOEL Nicosia who surprisingly top the group at the halfway point, by a point over Zenit St. Petersburg and Porto, with Shakhtar Donetsk sitting bottom but only three points back of the leaders.

Things could take quite a turn tomorrow night, with Porto going to Cyprus and Shakhtar. Porto might be the best team in the group, but APOEL are the only unbeaten team, which certainly can’t be dismissed. They’ve impressively ground out results thus far, coming back late to beat Zenit at home and impressively drawing at Shakhtar and Porto, so if they wind up qualifying or even winning this group, it shouldn’t be considered a surprise as it would’ve been initially.

Last but not least, in Group H, Barcelona and AC Milan, who both have seven points, will both qualify for the round of 16 with away wins over Viktoria Plzen and BATE Borisov respectively.

Wednesday

The two Manchester rivals are going to be in action on Wednesday, and both face must-win matches of differing difficulty.

While City are off to a real flyer in the Premier League, the same can’t be said for their first experience in the Champions League. At the halfway point, they sit third in Group A, three points behind leaders Bayern Munich and one behind second-placed Napoli. For all of their prolific scoring in the Premier League, they haven’t been able to replicate it in Europe, with only three goals in three matches.

The top two in the group face off in Munich on Wednesday, while Manchester City visit a severely injury-hit Villarreal side. Villarreal gave it all they had in Manchester two weeks ago, with City escaping with a 2-1 win thanks to Sergio Aguero’s last-gasp winner, so City can’t go in expecting an easy ride, even if Villarreal are as hobbled as they are.

If they fail to win in Spain, City will be up against it to qualify, even if Bayern extend their group lead by beating Napoli at home. City finish up with a visit to Napoli and a visit from Bayern, and getting even four points from those two matches will be a tough task.

In Group B, leaders Inter Milan will be after a third straight group win as they host Lille, while Trabzonspor and CSKA Moscow, who are both two points behind Inter, face off in Turkey. Inter are still barely treading water in Serie A, but they’ve gotten it right in Europe after being shocked at home by Trabzonspor in their opener, and they should move within touching distance of the last 16.

Despite being two points behind Benfica, Manchester United are still well-positioned to win Group C. United host Otelul Galati on Wednesday before finishing up with Benfica at home and Basel away, and if United play up to their capability and not down to the level of their competition as they sometimes appear to.

However, Benfica have to fancy their chances as well, as they have home ties against Basel and Otelul Galati sandwiched around their trip to Old Trafford. Will United’s home draw against Basel come back to bite them?

In Group D, it’s looking like a runaway win for Real Madrid, who are on nine points, with Ajax and Lyon, the two candidates for second, both on four. Real will book a place in the last 16 with a win at Lyon on Wednesday, and considering their 4-0 pasting of the French side at the Bernabeu and their current scintillating form, you’d have to favor that outcome.

However, if Lyon could top Real, they‘d be positioned to at least leave top spot up for grabs going into the final round of matches, since they finish up with Ajax at home and Dinamo Zagreb away. But even if Lyon lose and Ajax win this week, Lyon still can’t be counted out. Ajax finish up with a home tie against Real after their visit to the Stade Gerland, and their road to three points is a lot more difficult than Lyon’s road to the six points that would see them grab second.

All in all, it stands to be a very exciting round of matches in the biggest and best club competition in football.

For match previews, analysis, and statistics from all of this week’s Champions League matches, check out WhoScored.com.