MANCHESTER, England -- Here are three points on Lyon's 2-1 win over Man City in Group F of the UEFA Champions League.

1. City shocked in UCL opener

The Champions League group stage is often criticised for being too routine for the big boys, but this was an eventful, unpredictable contest that ended with a genuine shock result. Manchester City entered arguably as the favourites to win the entire competition, never mind this game, while Lyon have started poorly in Ligue 1. A comfortable home win seemed likely; an away win was what ensued.

The basic decision when analysing a shock result is simple: Was it the favourites performing poorly or the underdogs excelling? Here, it was a bit of both, combined with some good fortune. Lyon's goals, scored by Maxwel Cornet and Nabil Fekir, weren't exactly "always on the cards," but City never offered their usual levels of control and were always vulnerable to quick breaks, especially when Lyon moved forward to close down in midfield. Both goals came after Fernandinho conceded the ball cheaply, and consequently, Lyon got men forward into attack quickly.

With Pep Guardiola serving a touchline ban, City's tactical changes felt conservative and unadventurous, with assistant Mikel Arteta introducing the three obvious attacking options from the bench without a significant change of shape. City never rallied, the crowd never had a sudden roar in expectation of a comeback, and City didn't really create any clear-cut chances outside of Bernardo Silva's goal.

Group F is relatively weak, and Shakhtar Donetsk and Hoffenheim's 2-2 draw earlier in the day means City haven't lost significant ground in terms of qualification to the knockout stages. But this was a surprising defeat that means City will have to expend extra energy later in the group phase to ensure they finish top. It's notable, meanwhile, that in the Champions League era, no eventual champions have started the group phase with a defeat, and for City to fulfil their potential this season, they must change that stat.

Making the step up from the Europa League, Lyon announced themselves in style vs. star-studded City. Photo credit should read OLI SCARFF/AFP/Getty Images

2. City punished for their sloppiness

From the outset, Manchester City were sloppy. In front of a subdued Etihad with plenty of empty seats, there was no intensity in City's passing and no speed when they attempted to break. Raheem Sterling often led the charge solo, with Gabriel Jesus marked closely and City's midfielders labouring behind the ball. Without Leroy Sane and Sergio Aguero from the start, and Benjamin Mendy and Kevin De Bruyne for the entirety, City lacked their most direct attacking options.

What was particularly surprising, though, was the number of sloppy touches across the pitch. Sterling twice fluffed his lines when he'd worked the ball into a dangerous position, Kyle Walker played a dreadful square pass across the front of the defence which invited a quick Lyon break, then Delph and David Silva collided while battling for the same aerial ball. Fernandinho was twice guilty of poor touches in the buildup to Lyon's goals.

Such a dreadful first-half performance, and the two-goal half-time deficit, meant a big half-time team talk for Arteta, effectively making his managerial debut with Pep Guardiola serving a touchline ban. City are the masters of changing formation, but what would they do here?

Well, it took 10 minutes of the second half before things changed. Sane was introduced in place of the underwhelming Ilkay Gundogan and played on the left. Sterling switched to the right, Bernardo Silva dropped into midfield, and Delph moved inside into a central midfield role alongside Fernandinho. It was more of a classic 4-3-3, with width on both flanks.

Sergio Aguero replaced Jesus with half an hour remaining, but City's passing patterns didn't improve. They relied on long-range shots from Fernandinho, then Delph, and then Delph again, an attempt soundtracked by groans around the Etihad before he'd even struck the ball.

Sane, though, proved useful. His dribble down the left was followed by a simple pull-back to Bernardo Silva, who swept the ball into the far corner -- the two main beneficiaries of City's first substitution combining. Sane continued to look bright. His trickery from the left attracted three Lyon defenders. He knocked the ball into David Silva, who laid it back for Aguero to fire low, but straight at Anthony Lopes, who dealt with low shots excellently all night.

Arteta's final roll of the dice came with 15 minutes remaining: Sterling off, Riyad Mahrez on. The Algerian was dangerous down the right, attracting defenders before cutting inside and bending inswinging crosses toward the far post. One met the head of Sane, probably the wrong recipient, and his header was weak. City lack a classic Plan B to get on the end of crosses, but ultimately Guardiola's major concern will be that City's Plan A, usually so slick, was so ineffective here.

With Sergio Aguero on the bench, Raheem Sterling and Man City were not quite themselves in attack. Photo by Chloe Knott - Danehouse/Getty Images

3. Fekir shines in leading Lyon

Lyon's approach here was clear. Rather than taking the game to Manchester City, they intended to sit back, defend in two banks of four and then break quickly.

Memphis Depay, booed by the home supporters because of his Manchester United connections, led the line, sprinting into the channels. Behind him, Fekir found space away from Fernandinho, collecting second balls and driving forward. Out wide, Houssem Aouar charged up and down menacingly, while right-sided Cornet darted inside from the right into goal-scoring positions.

It was Cornet who had the fortune to be playing up against Delph, who endured a nightmare first half, and the right-winger proved Lyon's main goal-scoring threat. He had the ball in the City net midway through the first half, but the goal was correctly disallowed for offside.

Five minutes later, he opened the scoring. Fekir's left-wing cross forced Delph into a hapless air-kick, and the ball ran through to Cornet, who tucked it confidently into the bottom corner. City had been made to pay for their sloppiness.

Having started with a counter-attacking system, Bruno Genesio didn't need to change anything at 1-0, and Lyon continued to play on the break. Fekir became increasingly influential in a left-sided position, combining with Aouar and inviting Ferland Mendy forward on the overlap. He later produced the best moment of the first half with Lyon's second goal, almost out of nothing, driving forward and slamming a low, left-footed shot past Ederson from outside the box.

A 2-0 half-time lead, in truth, slightly flattered Lyon, but Fekir demonstrated precisely why so many of Europe's major clubs covet his signature. Wearing the captain's armband, Fekir is as much a leader as a technical talent, going around his teammates before the game and embracing each one in turn.

In this No. 10 role, he worked hard defensively and positioned himself intelligently at transitions. His upper-body strength means he can bounce off opposition challenges and win free kicks, and he found space between the lines when Fernandinho dropped into the defensive line when Lyon had goal kicks.

Meanwhile, Lyon could have extended their advantage after an hour when Depay raced onto Tanguy Ndombele's curled through ball, but his side-footed finish prompted Ederson to make an excellent save, turning the ball onto the post. In the end, they didn't need that third goal, but the fact they created the second half's best chance illustrates that this could have been 1-3 as easily as it could have been 2-2.