Champions League: Lamine Yamal scores as Barcelona defeat Arsenal as they move up a point in Italy

Matchday 1 of the new, expanded and revamped UEFA Champions League first round concluded on Thursday with the final 12 entrants making their debut in the 2024-25 version of football's most prestigious club competition.

Here are the biggest takeaways from Thursday's six-game schedule.

Raya's stops give him a point Arsenal: Atléti get a late victory

After reaching the quarter-finals last season (their first in the Champions League after a five-year break) and finishing as runners-up in England for two seasons running, Arsenal are intent on winning at least one of the two trophies in 2025. They were lucky to pick up even a single point at Atalanta on Thursday night.

If goalkeeper David Raya had not stopped Azurri Striker Mateo Retegui scored two goals in succession in the second half, one from the penalty spot and another from the rebound, and the Gunners would have left Italy empty-handed.

It looked like Atletico Madrid would also settle for a draw, which would not have been the worst result, even at home, after RB Leipzig scored four minutes into the game. Antoine Griezmann canceled The result was positive, but the score was still tied in the 90th minute. Fortunately for Atleti, Uruguayan centre-back José María Giménez headed in the winning goal just as second-half added time was about to begin, infuriating the home fans. Wanda Metropolitano Stadium in ecstasy:

It was likely to be a long night for Barcelona after defender Eric Garcia received a direct red card Less than 10 minutes into Tuesday's trip to Monaco, and that was before the hosts took a 1-0 lead in the first half.

But Barca were in fairly good form after 17-year-old star Lamine Yamal drew his side level in the principality with a superb equaliser, his first in the Champions League.

The goal made Yamal the second-youngest scorer in the tournament's history after teammate Ansu Fati (Fati would come on as a substitute later in the game), and Hansi Flick's side did well into the second half. However, everything changed just over a quarter of an hour from time when Monaco substitute George Ilenikhena surprised the Spanish defence and scored what turned out to be the winner past veteran Barca goalkeeper Marc-André ter Stegen. It was Barcelona's first competitive defeat under new coach Flick.

Bayer Leverkusen Picks up right where it left off

The German champions went almost the entire 2023-24 European season unbeaten, remaining unbeaten on their way to the Bundesliga title and losing only the final game of their 51-match campaign, to Italian side Atalanta in the UEFA Europa League final.

Leverkusen have already lost one Bundesliga game this season but having already reached the Champions League this term, Xabi Alonso's side got their international campaign off to a flying start by beating Dutch side Feyenoord 4-0 away on Thursday.

Germany striker Florian Wirtz opened the scoring in Rotterdam after just four minutes. Left-back Alejandro Grimaldo doubled his side's lead before Wirtz scored Leverkusen's third shortly before the break.

An own goal before half-time made it 4-0 and the visitors never looked back.

With their first ever domestic crown secured, Alonso can now turn the attention of all his players to making a big run in Europe next spring. With a trip to Bayern Munich at the end of the month and their next Champions League test against seven-time champions AC Milan, we'll soon see if they are legitimate contenders.

Doug McIntyre is a soccer journalist for FOX Sports. A former writer for ESPN and Yahoo Sports, he has covered the U.S. men's and women's national teams at FIFA World Cups on five continents. Follow him on @By Doug McIntyre.