For a while in the first half at Stamford Bridge it was tempting to dig out the old blurred distinction between a good general and a lucky one. In need of a lift after a fretful opening half-hour, José Mourinho's Chelsea-in-progress ended up making serene progress to the verge of the Champions League knockout stages thanks, in the first instance, to a piece of wonderful opportunism from the Douala pickpocket, Samuel Eto'o. The Cameroonian scored twice, his first a work of pure cheek (Mourinho called it "a fox goal"), his second perhaps more significant in the long run, involving a sweeping interchange with his fellow Anzhi Makhachkala old boy Willian and providing in the process a first real big-match glimpse of genuine Eto'o quality in a Chelsea shirt.

If the opening goal was vital, it was also a lovely moment for Eto'o, scourge of the sweeper-keeper, who seems to be developing something of a habit for this kind of thing. Controlling a back pass under no pressure Timo Hildebrand decided to take a moment to sniff the air, shuttling sideways, waggling a foot over the ball and remembering only as Eto'o closed in with malevolent intent that he is not in fact Xabi Alonso after all. Panicked, Hildebrand scuffed his clearance against Eto'o's foot, which was already raised like a volleyball player's palm to deflect it back into the net.

Eto'o celebrated as if he meant it and who can doubt that he did, given his purse-snatch of an assist against Cardiff City last month. There was also a prolonged hug for Mourinho, who had until then been a slightly fraught figure, stalking the touchline in his padded gown, repeatedly gesturing for more pep, more vim, more drive. Eto'o, a genuine prince of the modern game, has now scored in nine separate Champions League seasons and for four different clubs overall in the competition.

If Chelsea were a little edgy at the start this was unsurprising. After the jarringly supine defeat at Newcastle United, Mourinho delivered a reassuringly dramatic coup de team-sheet here, making six outfield changes and in the process providing a glimpse of the bewildering variety of personnel available to him: his starting XI here was signed by eight different Chelsea managers, including Mourinhos Mk I and II.

Most intriguingly there was a start in a vital match for Chelsea's Dagestan duo. Eto'o in particular has been a puzzling figure this season, a veteran of three winning finals in this competition but at the same time an ageing close-season panic signing who remains Chelsea's chief central attacker in Fernando Torres's absence – albeit backed up here by Demba Ba, who lurked on the bench like a forgotten winter coat grudgingly retrieved from the back of the wardrobe, before emerging to score a fine third goal.

For 20 minutes either side of half-time there was evidence Eto'o may yet have the drive to recover from what Chelsea's manager has identified as a special kind of lassitude induced by exposure to the cowboy plenitude of the Russian league. "When you play without big motivations you train without big motivations, you lose condition," Mourinho said afterwards. "But step by step he is learning. He is a naturally fit guy."

Willian also started to complete an improbable 12 months in his own career. It is almost a year ago to the day since Willian scored twice and looked a star in the making as Shakhtar Donetsk lost 3-2 at Stamford Bridge. Signed by Anzhi in January, he stayed in Dagestan long enough to emerge a noticeably less svelte darting inside-forward in his first few appearances at Chelsea. There have been some consolations, though: pretty much invisible to Brazilian TV audiences during his glory years in Russia, he now finds himself in Luiz Felipe Scolari's national squad on the back of the odd flicker in the Premier League.

Here Willian recovered from a slightly bewildered start. His first three contributions were kicking the ball out of play, falling over and passing to Julian Draxler, a spindly figure, with an air of knock-kneed frailty for all his height, but a player who demonstrated a wicked way with a pass in the opening half-hour as a physically impressive Schalke hurried Chelsea.

Either side of his goal Eto'o prowled the periphery. He may lack the preternatural spring of old but he remains a lovely mover. When he cut inside after Willian's burst through the middle on 54 minutes, his finish into the far corner was instant and unanswerable. Mourinho may be sifting through the elaborately talented oddments of a curious squad but in Eto'o – given a standing ovation as he left the pitch after 77 minutes – he has a source of enduring incision.