Following some interesting results and surprise victories on the opening Champions League matchday, there are some particularly intriguing fixtures this week -- and some exciting individual matchups.
Here are four key battles that could prove crucial in deciding the outcome of the most interesting games:
Thiago Motta (PSG) vs. Sergio Busquets (Barcelona)
These two have history. Motta was sent off in the famous 2010 European Cup semifinal between Pep Guardiola's Barcelona and Jose Mourinho's Inter, courtesy of Busquets' infamous theatrics having been gently touched in the face.
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Being sent off at the Camp Nou was an enormous setback for Motta, who trained at Barcelona as a teenager but failed to make a significant contribution in the first team. Furthermore, while Inter fought impressively with 10 men and recorded an aggregate victory, Motta was suspended for the final win over Bayern Munich.
Motta has impressed for PSG over the past couple of seasons, although his 2014-15 displays have been underwhelming, in keeping with those of his teammates. When on form, Motta is a strong, powerful player in the tackle and commanding in the air -- but also capable of playing intelligent passes into attack and swinging in dangerous set-pieces. Busquets plays a more reserved role, but few players are as capable of commanding a midfield zone. There might not be many direct confrontations, but whoever performs better will put his side in control.
Paris and Barcelona were drawn together in the Champions League quarterfinal two seasons ago, with Barcelona winning on away goals, but Motta and Busquets didn't face each other; Motta missed the first leg, Busquets the second.
At international level, they have often managed to avoid each other. In Italy and Spain's two Euro 2012 meetings, Motta was introduced after 89 minutes of the group match and limped off a couple of minutes into his appearance in the final (when his tactical task was supposed to be pressing Busquets energetically from an advanced midfield position). They did both start in Spain's 1-0 friendly win over Italy earlier this season, but a first competitive meeting since that Camp Nou incident is Motta's perfect opportunity for revenge.
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Yaya Toure (Manchester City) vs. Seydou Keita (Roma)
Yaya Toure was criticised heavily in the wake of City's narrow defeat to Bayern Munich, and he's certainly due a good performance this week.
The Ivorian is considered a midfielder for the big occasions, constantly producing crucial goals throughout his City career, particularly in the period when they were unaccustomed to winning trophies. Rarely, however, has he performed in the Champions League. This should be an excellent opportunity for him to set the record straight.
Roma are without their two strongest midfielders -- vice-captain Daniele De Rossi and long-term injury victim Kevin Strootman -- and while Rudi Garcia can count upon depth in that position, his weakened midfield trio might find themselves overrun.
Miralem Pjanic will play to the right, and is capable of creating chances with his excellent passing skills. He also offers a great set-piece threat. Radja Nainggolan will also have an important role, powering forward to connect defence and attack. The man tasked with stopping Toure, however, will be one of his ex-teammates.
Seydou Keita played alongside Toure in the Barcelona midfield, and was a favourite of Pep Guardiola for his reliable, professional and committed approach to the game. Although often used as a box-to-box midfielder at Barca, he's likely to play the De Rossi role here, protecting the defence. It's not his natural position, but Keita has the positional awareness and the strength to cope with Toure's typical powerful midfield runs. If Toure is quiet yet again, expect more media focus upon his disappearing act in European competition.
Alexis Sanchez (Arsenal) vs. Alex Telles (Galatasaray)
Arsene Wenger surprisingly decided to leave Sanchez on the bench for the north London derby on Saturday, although the Chilean forward was introduced midway through the second half and was involved in Alex Oxlade-Chamberlain's equaliser. The obvious assumption is that Sanchez was being rested for this week's crucial Champions League clash with Galatasaray.
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Upon Sanchez's arrival, Wenger insisted the Chilean would play upfront as frequently as on the flank, but the purchase of Danny Welbeck means the manager might deploy him wide more regularly than anticipated. Currently, his regular role is as an attack-minded, outside-right winger.
In Galatasaray's left-back zone, Cesare Prandelli has two options. He could use veteran Hakan Balta, a dependable performer but probably too slow and technically limited for the style of football Prandelli preaches.
Instead, Brazilian Telles should start -- and he's as Brazilian a full-back as you'll find. Speedy going forward on the overlap and a genuinely creative player in the final third, Telles remains defensively suspect, leaving too much space between he and left-sided center back Semih Kaya.
That, worryingly, is exactly the zone Sanchez loves to work in. Expect something of a cat-and-mouse battle between the South American duo. It will be interesting to see how much Sanchez tracks back and how much he remains in a position to attack. Goals should originate from this zone.
Karim Bellarabi (Leverkusen) vs. Eliseu (Benfica)
Bellarabi has been on the periphery of the Bayer Leverkusen side for a few campaigns -- sometimes injured, sometimes out on loan, sometimes simply a squad player. This season, however, he has become one of the key performers in Roger Schmidt's exciting, heavy pressing side and could dominate this week's meeting with Benfica.
Bellarabi began his campaign with a goal after just nine seconds -- the fastest in Bundesliga history -- in the 2-0 victory over Dortmund on the opening day, starting as he intended to continue. Although generally fielded on the right of a 4-2-3-1, he drifts across the pitch into central and left-sided positions, and his combinations with impressive No. 10 Hakan Calhanoglu look particularly dangerous.
Benfica's Eliseu is another full-back more concerned with attacking than defending. His contribution in the opposition half is often spectacular; two years ago this week, for example, he netted a superb double for Malaga against Anderlecht in this competition. He might not be allowed many opportunities to scamper forward, however, and will instead be pinned back by Bellarabi as part of Leverkusen's commitment to press. When on the back foot, Eliseu can look extremely nervous, and Bellarabi might continue his fine start to the campaign.