Running analysis from Champions League's opening week

The Champions League is back! theScore is providing key takeaways from Matchday 1 of this season's competition, which runs through Thursday. Check in all week for updated thoughts and analysis from the marquee matches.

Arsenal boast serious strength in depth

Mikel Arteta must feel pretty clever. Gabriel Martinelli scored 36 seconds after replacing Eberechi Eze at San Mames, squeezing a shot through Athletic Bilbao's Unai Simon after impressively settling a lofted pass with a series of neat touches as he sprinted toward goal. And the assist came from Leandro Trossard, who'd only been on the pitch for around seven minutes.

The effectiveness of Arteta's second-half changes was further emphasized when Trossard put the result beyond doubt following a Martinelli cutback. Arteta calls his substitutes "finishers" for a reason.

The 2-0 victory owes plenty to Arsenal's squad building in recent transfer windows. Last season, traveling to a tricky away day without Bukayo Saka and Martin Odegaard would've caused concern. But now the Gunners can lean on their much-improved depth with greater confidence. Arsenal pulled off a similar trick over the weekend, easing to a 3-0 win over Nottingham Forest while Declan Rice started on the bench. Resting the English midfielder was a luxury that Arsenal couldn't afford before this summer.

"The Kylian Mbappe team"

Pep Guardiola caused controversy when he referred to Tottenham Hotspur as "the Harry Kane team" in October 2017. He might need to restrain himself from leveling a similar accusation at Real Madrid when Manchester City travel to the Spanish capital in December.

Kylian Mbappe saved Los Blancos from making a poor start to the league phase, scoring both goals from the penalty spot in a 2-1 win over Marseille. Real Madrid were uncharacteristically rattled during the match. Dean Huijsen lost his cool after a hack from Pierre-Emerick Aubameyang, and Dani Carvajal, who came on for an injured Trent Alexander-Arnold, was sent off for thrusting his head toward goalkeeper Geronimo Rulli. This isn't the first time Mbappe has carried his team this season: His spot-kick earned an unconvincing narrow victory over Osasuna in Madrid's La Liga opener, and he inspired his side to three points Saturday against Real Sociedad.

Madrid mostly relying on one player isn't sustainable - even if that player is as good as Mbappe. Jude Bellingham is back in contention after his shoulder surgery, so Xabi Alonso will be hoping the Englishman, along with Vinicius Junior, Rodrygo, and his other attackers, can quickly find some consistency and lighten Mbappe's load.

Juve playing with fire

For better or worse, Juventus might be the most entertaining team in Europe right now. Who expected that coming into the season? The Bianconeri followed up Saturday's manic 4-3 league win over rivals Inter Milan with an equally surreal draw against Borussia Dortmund. All eight goals Tuesday came in the second half, including a Kenan Yildiz stunner and Juve's two stoppage-time tallies that turned what looked like a surefire loss into a potentially important point come the end of the league phase.

The exhilarating finish once again showed the squad's never-say-die attitude, but it's also not a recipe for sustained success. If you have to score four goals every time you step on the pitch to win - or even just draw - you're going to be in big trouble when the goals inevitably dry up. "If we continue to concede goals like we did tonight, we'll never see the end," manager Igor Tudor, a former defender, correctly observed after the breathless stalemate.

The current iteration of this team is almost unrecognizable for a club that's historically had success building from the back outward. That's somewhat by design after a summer spent overhauling the attack and retaining Dusan Vlahovic, who's started the season like a house on fire and inspired Tuesday's late comeback. But this top-heavy squad needs to find some balance, especially with a trip to Real Madrid on the horizon in the league phase.

Underdogs have their day

Royale Union Saint-Gilloise and Qarabag both made history Tuesday.

Union's rise has been meteoric. They were promoted to Belgium's second division in 2015 and into the Belgian Pro League in 2021 before winning the country's top domestic cup in 2024 and conquering the first tier a year later. It's not over: Union won their Champions League debut at Dutch titleholders PSV Eindhoven with a scarcely believable 3-1 victory.

Qarabag appeared in the Champions League group stage in 2017, taking two points from Atletico Madrid but getting nothing from their matches against Chelsea and Roma. Finally, they got their first Champions League win - and the first for an Azerbaijani team - after fighting back from down 2-0 to win 3-2 at Benfica. The result marks just the second time that the Portuguese giants have lost a Champions League match after holding a two-goal lead, with the previous occasion happening only in January against Barcelona.