Believe it or not, by the time this week ends, the UEFA Champions League and Europa League group stages will already be halfway done.

Here’s your guide to how to watch the action, plus a MLS game that will have big implications for the Union.

Shakhtar Donetsk vs. Borussia Mönchengladbach

Tuesday, 12:55 p.m. (Galavisión, CBS All Access)

These are the top two teams in a group that also includes heavyweights Real Madrid and Inter Milan. If Shakhtar wins this game, the Ukrainian club will take a huge step toward booking a spot in the round of 16. Watch out for 20-year-old Brazilian winger Tetê and 21-year-old Israeli winger Manor Solomon, who sparked the group stage-opening upset of Madrid and a scoreless tie with Inter.

Mönchengladbach is again led by Marcus Thuram, who has two goals and an assist in the tournament so far.

Real Madrid vs. Inter Milan

Tuesday, 3 p.m. (UniMás, TUDN, CBS All Access)

When Real Madrid is in crisis, it’s often a crisis that the rest of the soccer world would love to have. The Spanish superpower can have just about any players and coaches it wants, and plenty of clubs would be thrilled to reach the European Cup once — never mind win it 13 times, as Real has.

So is it a crisis for Real to be in last place in the group through two games, with a loss at home and a tie on the road? Of course it is. And Inter, another favorite to win this season’s tournament, is barely better with two ties.

Unless Shakhtar collapses, one of these two teams is going to crash out at the end of the group stage. And if Real doesn’t win this game, it could be the one.

Atalanta vs. Liverpool

Tuesday, 3 p.m. (CBS All Access,

CBS Sports Network’s whiparound show (and Univision’s online whiparound show) will be especially helpful on Tuesday, because this game is also brimming with potential. Atalanta has been one of the most fun teams to watch in Europe over the last few seasons, led by forwards Papu Gómez, Luis Muriel and Duván Zapata. The Italian club is flying again this campaign, averaging 2.9 goals per game across Serie A and the Champions League.

Liverpool, meanwhile, is riding a five-game unbeaten streak in all competitions, made even more impressive by star centerback Virgil van Dijk being out for the season with an ACL injury.

Istanbul Başakşehir vs Manchester United

Wednesday, 12:55 p.m. (UniMás, TUDN, CBS All Access)

Good luck to anyone who thinks they can figure out United these days. The club’s last four games have been a 2-1 upset win at Paris Saint-Germain, a scoreless draw against Chelsea at home, a 5-0 rout of RB Leipzig at home, and a 1-0 loss to Arsenal at home.

Now the Red Devils go on the road to Istanbul, where last Wednesday Başakşehir held PSG scoreless until the 64th minute in a 2-0 loss. Paul Pogba and Marcus Rashford will go up against a pair of players well-known to United fans, former Liverpool centerback Martin Skrtel and former Newcastle and Chelsea forward Demba Ba.

RB Leipzig vs. Paris Saint-Germain

Wednesday, 3 p.m. (CBS All Access,

When this group drawn, the theory was that PSG was the favorite and Leipzig stood a chance of beating Manchester United to second place. It may yet play out that way, but for now, both of these teams have a loss to United on the books. Plenty of American eyes will be on Leipzig’s Tyler Adams, who has been recovering from a knee injury and is almost back to playing shape.

PSG will be without a slew of injured stars, including Kylian Mbappé. He joined joined Neymar, Marco Verratti, Mauro Icardi and Julian Draxler on the sidelines this week.

Orlando City vs. Columbus Crew

Wednesday, 7:30 p.m. (ESPN+)

Union fans will want to watch this game, because an Orlando win or tie will knock Columbus out of the Supporters' Shield race. Columbus is in third place and Orlando is in fourth, both with 38 points, and New York City is on their tails in fifth with 36. The third and fourth place finishers get to open the playoffs at home.

» READ MORE: The Union scored just once on 22 shots vs. Columbus, so of course fans are blaming Joe Bendik

Real Sociedad vs. AZ Alkmaar

Thursday, 12:55 p.m. (CBS All Access,

AZ surprisingly leads its Europa League group after an upset win at Napoli to start the stage. The Dutch club then thumped Croatia’s HNK Rijeka 4-1 at home last Thursday. This game will be another test for a club that features veteran Dutch national team centerback Bruno Martins Indi , on loan from Stoke City; and promising 22-year-old midfielder Dani de Wit, who grew up in Ajax’s youth academy.