Champions League Matchday 3: 6 Key Battles to Watch

The UEFA Champions League is back, and the action is heating up as the group stage reaches its midway point this week.

Eight matches are scheduled for Tuesday, with eight more Wednesday. All of the games will feature intriguing and compelling individual matchups, but some will stand out from the rest.

Here are six key matchups to look out for on Champions League Matchday 3.

Barcelona's Defensive Crisis vs. Celtic

Details: Barcelona vs. Celtic, Group G, Tuesday, 2:45 p.m. ET

Where they stand: Barca lead Group G with six points from two matches. Celtic are second with four.

Barcelona defender Carles Puyol (pictured, left) is out for eight weeks after mangling his elbow in a scary fall earlier this month (via The Guardian). He won't play in Barcelona's home match against Scottish champions Celtic on Tuesday.

Puyol's central-defensive partner, Gerard Pique, is still recovering from a foot injury and is also expected to sit out the match (via The Sun).

That leaves Barca with a probable central-defensive partnership of Javier Mascherano and Alex Song. With full-back Dani Alves also injured, Martin Montoya is expected to start on the right.

Meanwhile, defensive midfielder Sergio Busquets is suspended after drawing a red card against Benfica in Barca's previous Champions League match.

Normally, Celtic wouldn't stand much of a chance against Barcelona's mighty possession game. That might still be the case Tuesday, considering the match will be played at Barca's intimidating Camp Nou, but Celtic might never have a better chance for a big European upset.

Franck vs. Franck

Details: Lille vs. Bayern Munich, Group F, Tuesday, 2:45 p.m. ET

Where they stand: Lille are last in Group F with two defeats and no points through two games. Bayern are tied for second with three points.

When Bayern Munich visit Lille on Tuesday, the game could be described as a showdown between Bayern's domestic and European form.

At home, the Bavarians have won a record-setting eight straight matches to begin the Bundesliga season. In Europe, they struggled to kill off the game against Valencia at home, then lost at Belarusian minnows BATE Borisov.

With that said, we'll opt for Franck vs. Franck as the key matchup. That's Bayern's Franck Ribery vs. Lille's Franck Beria.

Beria often plays on the left, but he is expected to feature on the right side of Lille's defense to fill in for the suspended Mathieu Debuchy. If he plays there, Beria will have to deal with the speed, trickery and guile of Ribery on Bayern's left flank.

That battle should be a win for Bayern. But then again, Bayern should have beaten BATE handily.

Eliseu vs. Abate

Details: Malaga vs. AC Milan, Group C, Wednesday, 2:45 p.m. ET

Where they stand: Malaga lead Group C with six points from two games. Milan are second with four.

AC Milan have probably been the most disappointing European powerhouse of the season so far. After finishing second in Serie A and advancing to the Champions League quarterfinals last season, the Rossoneri lost superstars Zlatan Ibrahimovic (a striker) and Thiago Silva (a defender) to big-spending Paris Saint-Germain in the offseason.

Without that influential duo, Milan have fallen astoundingly to 15th place in the Serie A table through eight matches. Defender Ignazio Abate says the Rossoneri must "man up" (via ESPN FC), and they'll have a chance to do just that Wednesday against Group C leaders Malaga.

The Spaniards are making the most of their debut season in Europe's premier club competition with two impressive wins in their first two matches. Among the several heroes (a list that must start with stylish midfielder Isco) has been Portuguese winger Eliseu, who thumped home a powerful volley last time out against Anderlecht (video at left).

If Eliseu starts on the left side of midfield, he'll likely come up against—you guessed it—Abate.

Time to man up, it seems.

The Armenian Marksman vs. the Russian Oil Money

Details: Shakhtar Donetsk vs. Chelsea, Group E, Tuesday, 2:45 p.m. ET

Where they stand: Chelsea lead Group E with four points and a plus-four goal differential. Shakhtar are second with four points and a plus-two differential.

Henrikh Mkhitaryan is one of the hottest scorers in Europe.

The Armenian midfielder has scored 14 goals during Shakhtar's amazing run of 12 straight wins to start the Ukrainian Premier League season. He has also scored twice in Shakhtar's first two Champions League matches this term.

Now comes Mkhitaryan's biggest test of the season so far: two matches against Chelsea's stout defense.

The Blues have allowed an English Premier League-best six goals while storming to the top of the table after eight matches. Captain and influential John Terry will be available despite serving a domestic suspension, so Chelsea should have a full-strength defense.

Not to mention a set of creative playmakers who are absolutely purring right now.

Manchester United Against Braga vs. Manchester United Looking Ahead to Chelsea

Details: Manchester United vs. Braga, Group H, Tuesday, 2:45 p.m. ET

Where they stand: United lead Group H with six points from two matches. Braga are tied for second with three.

Manchester United should win this game. Full stop.

Trouble is, there's a big, big league match looming at the weekend. United are set to play at league-leading Chelsea on Sunday, and a victory at Stamford Bridge would pull the Red Devils within one point of the table's summit.

And yes, United will be looking ahead. First-choice defenders Rio Ferdinand and Patrice Evra will be rested against Braga (via ManUtd.com), and that means untested defenders Scott Wootton and Alexander Büttner could start.

Even so, United should have enough firepower to win this match. Still, this one might be worth keeping an eye on.

Marco Reus vs. Real Madrid's Defense

Details: Borussia Dortmund vs. Real Madrid, Group D, Wednesday, 2:45 p.m.

Where they stand: Real Madrid lead Group D, the so-called "Group of Death," with six points from two matches. Dortmund are second with four.

Mouthwatering matchups will abound when two-time defending German champions Borussia Dortmund host Spanish champions Real Madrid on Wednesday in the Group of Death.

Dortmund, and in particular right-back Lukasz Piszczek, must find a way to defender Portuguese superstar Cristiano Ronaldo. Real's midfield must deal with the budding creativity of German wunderkind Mario Götze.

But the player who reportedly has Real Madrid manager Jose Mourinho worried is Borussia Dortmund midfielder/forward Marco Reus. As Spanish paper Marca reports:

"

He is a player with a direct playing style, with a great turn of speed and a good shot. He plays in behind the centre forward Lewandowski in the German national team, in front of Özil, as a second striker together with Klose. His speed, mobility and shooting power make him a player who is difficult to mark, as he surprises everyone, coming up from behind, and with long shots. He has a nose for goal.

"

That description is based mostly on Reus' performances with the German national team. But Reus has been no slouch in his first season with Dortmund, having scored four goals and assisting two more in eight league appearances.

Stopping Reus could be key to Real maintaining their 100 percent Champions League record intact.

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