A look at what's happening in the Champions League on Tuesday:

GROUP A

European champion Bayern Munich is cruising toward a spot in the knockout stages after beating Atlético Madrid and Lokomotiv Moscow, and next up is Salzburg. The Austrian club has one point from two games. However, there are reasons for Bayern to be concerned. Bayern looked fatigued in its 2-1 wins over Lokomotiv and Cologne last week and squad issues are once again in focus after club president Herbert Hainer said a new contract for David Alaba is off the table after talks broke down. Salzburg won plaudits for its combative approach against another European champion, Liverpool, last season in a 4-3 loss and coach Jesse Marsch wants another brave showing. "Aggressive is always better than passive," he said on Monday. Atlético heads to Russia to face Lokomotiv in the other game.

GROUP B

Last-placed Real Madrid is approaching the match against Inter Milan as a final after starting its campaign with a home loss to Shakhtar and an away draw against Borussia Mönchengladbach. Another setback could jeopardize Madrid's chances of advancing and lead to its first group-stage elimination in three decades. The teams which caused problems for Madrid meet as Shakhtar Donetsk hosts Borussia Mönchengladbach in Ukraine. Gladbach tried to emulate Shakhtar with a surprise win over Madrid last week but had to settle for 2-2 after Madrid's Casemiro scored in stoppage time.

GROUP C

Marseille's return to the Champions League is turning into a bitter experience. Back in the elite tournament for the first time in almost seven years, the 1993 European champion travels to Porto looking to avoid a third consecutive loss. Undone by a flurry of individual errors, Andre Villas-Boas' side was overrun by Manchester City at the Velodrome in a 3-0 loss during its previous outing. The Marseille coach has been given a few extra days to fix the problems and get his players ready for Porto after a coronavirus outbreak forced the postponement of their French league game. City goes for a third straight win when Olympiakos visits Etihad Stadium, with the English team still likely to be without its two strikers — Sergio Aguero and Gabriel Jesus. Jesus is back in light training, however.

GROUP D

Atalanta coach Gian Piero Gasperini is looking for a result from one of its two matches against Liverpool to stand it in good stead for its final group match showdown against Ajax. Liverpool tops Group D with six points, two more than Atalanta and five more than Ajax. Midtjylland is bottom with zero points. Gasperini expects Liverpool to finish top of the group and for Atalanta to battle with Ajax — a surprise semifinalist two seasons ago — for the second qualifying spot. After the doubleheader against Liverpool, Atalanta hosts Midtjylland before traveling to Ajax for their potentially decisive final group match. Ajax has traveled to Denmark with just 17 players to face Midtjylland, including Kjell Scherpen as the only goalkeeper. Scherpen has not played a first-team game for Ajax since joining the club last year.