Nkunku and Madueke give Chelsea first-leg advantage against Servette | Europa Conference League

It was not exactly all sweetness and light for Chelsea during this ­prosaic 2-0 win over Servette. Those ­hunting for optimism could find it in ­encouraging displays from some new faces, while goals from ­Christopher Nkunku and Noni Madueke during an improved second half should ensure that progress to the Europa ­Conference League is secured in ­Switzerland next week, but there were also moments when discontent in the stands bubbled to the surface.

There was a fair bit of unrest after a torpid opening period, ­during which it was hard to see why Mykhailo Mudryk has been preferred to Raheem Sterling in attack, and later there would even be hints of opposition to Enzo Maresca’s style of play. It was certainly odd to hear boos when Moises Caicedo, who was under pressure, turned backwards in possession.

Shouldn’t keeping the ball be applauded? Maresca must have been exasperated, especially as Madueke would soon round off a flowing move that began with a ball out of defence a few minutes later. After a year out of Europe, Chelsea had taken a big step towards securing their spot in this season’s group stage.

Events have moved so quickly at Stamford Bridge that even the ­editors of the matchday programme for this tie were beaten by the decision to hand Sterling’s No 7 shirt to Pedro Neto. A mess, though? Not ­according to Maresca. He says that he has his preferred group of players and the harsh reality is that nobody could be surprised that Ben Chilwell and ­Sterling were absent again, along with all the other outcasts in a squad that needs heavy trimming before next week’s transfer deadline.

There is much work to do, on and off the pitch, and the pace of change has been dizzying. There was time before kick-off for a brief sighting of João Félix, who beat the badge on his chest as he was paraded before the crowd after his arrival from Atlético Madrid, and Chelsea tried to make a decisive start. Marc Guiu, an ­18-year-old forward who was one of six players making his full debut, went close after being released by Kiernan Dewsbury-Hall, a Maresca stalwart who was crucial for the Italian when he led Leicester to the Championship title last season.

Things looked promising for the first five minutes or so but soon ­quietened down. There were a few bustling runs from Guiu, but rough edges to his game were evident and he was not the only forward to struggle for consistency. Christopher Nkunku was quiet, Neto did not see enough of the ball on the right and Mykhailo Mudryk, who spurned Chelsea’s best chance of the first half, continued to resemble an enigma on the left flank, so much so that there were howls of frustration when the Ukrainian wasted a counterattack by passing straight to a visiting defender.

Apparently this is Maresca’s type of winger. While there is no space for Sterling, Mudryk is still being given time to find his feet and live up to his fee. His issue, though, is that ­everything is scattergun; his half was summed up by the moment when, having beaten Keigo Tsunemoto with nifty footwork, he knocked the ball behind for a goal kick.

No wonder Servette, who finished third in Switzerland last year, made it to half-time unscathed. They were holding Chelsea at arm’s length and had even threatened on the break. Filip Jörgensen, a new signing from Villarreal, was required to push Dereck Kutesa’s shot over after ­Chelsea were cut open on the left.

Chelsea walked off to loud boos. They had to lift the mood. Pressing higher and with more urgency, they made the breakthrough at the start of the second half. Guiu forced an error from Servette and ­Dewsbury-Hall released Nkunku, who went through, touched the ball past Jérémy Frick and tumbled to ground after being caught by the Servette goalkeeper.

The tension evaporated. Nkunku buried the penalty and Chelsea set off in pursuit of a second goal. There was an extraordinary moment when Frick suffered another loss of­ ­composure and had to race back after being ­dispossessed by Guiu, only for the eager youngster to fail to take ­advantage despite being given two opportunities to shoot from close range.

More chances came and went. Maresca needed more ruthlessness and there was a huge roar of approval when Cole Palmer came off the bench. The home fans also seemed to enjoy how Renato Veiga, a versatile 21-year-old signed from Basel, fared at left-back.

Chelsea had more to give and they pulled clear when two substitutes combined, Enzo Fernandez finding Madueke, who burst through before crashing a powerful shot inside Frick’s near post.

It was a fine goal, although Maresca will not like how his side dozed off during the dying stages. Servette went close to pulling one back on several occasions. There is still work to do.