Strolls such as this offer timely reminders that, for all the upheaval of recent weeks, Chelsea will still ease into the second half of the campaign in rude health. Very few teams can boast comparable strength in depth, even after the sale of a World Cup winner for £37.1m. Manchester City will presumably test that theory in the fifth round more concertedly than Stoke City did in the fourth.

If the scoreline suggested this was a squeeze, it was actually a breeze. José Mourinho, celebrating his 51st birthday, could bemoan familiar profligacy as having denied his team proper reward for their dominance, and this side's failure to convert the plethora of chances they invariably create could yet undermine a pursuit for silverware that is maintained on three fronts.

But that was just the perfectionist in him exposed. Stoke, for all their success in avoiding the concession of a cricket score, never threatened to take advantage of the slenderness of their deficit.

Progress, courtesy of Oscar's sumptuous free-kick, ensured there was to be no mass gnashing of teeth at Juan Mata's sale to Manchester United. The departed midfielder was the elephant in the room here, the Spaniard the subject of one small banner held up by supporters in the west stand thanking him for two and a half years of fine service but, if truth be told, he was not overly missed. Perhaps it was not the contest by which to judge his departure but, without him, and with Michael Essien to join Milan and Kevin de Bruyne now at Wolfsburg, the hosts merely rejoiced in the excellence of the creative talents that remain. Or, even, in confirmation of Mohamed Salah's £11m arrival from Basel and the leggy purpose of Nemanja Matic in central midfield.

This was the £20.75m Serb's first start in two spells at this club and his physical presence and ability to stride forward with purpose stamped authority on the occasion. He is already unrecognisable from the wiry youth who had mustered three substitute appearances in 2009-10.

"He was very comfortable, offering big stability," said Mourinho. "I have no statistics but he stole a lot of balls and his passing was always quality. His left foot is soft. The ball comes always sweetly and the decision is always an easy, simple decision. The team flies when somebody makes it so simple."

He was progressive in his passing, too, to suggest he will offer another dimension. Once Mourinho has tweaked his forward ranks in the summer, with funding bolstered by Mata's sale, his lineup could indeed be the "phenomenal" selection he had confidently predicted a few weeks ago. The evolution is being played out in the public glare this term.

Stoke, once Peter Crouch had nodded wide five minutes in, failed miserably to check it. Even in the last 10 minutes, when their resistance – personified by the excellence of Ryan Shawcross and Asmir Begovic – had earned them a chance to pour forwards in search of parity, they mustered little of note.

They can concentrate now on securing top-flight survival, with Cardiff's Peter Odemwingie to join on Monday as Kenwyne Jones heads in the opposite direction.

The Nigerian will inject much needed pace into their front-line. Mark Hughes admitted they had not "forced the issue enough" though, in truth, they were too preoccupied trying to keep the home side at bay. Hazard is irrepressible these days, his burst of pace across the turf and quality in touch and vision illuminating his side's approach on a weekly basis. The Belgian might have conjured rewards for Frank Lampard and Oscar, while quite how neither Samuel Eto'o nor the substitute Ramires could score from inside the six-yard box after another fizzed centre defied belief. Oscar and André Schürrle crunched shots across the woodwork and, when David Luiz thrashed a free-kick goalwards late on, Begovic summoned a fine reflex save that took the breath away.

Another Brazilian had already beaten him from a dead-ball by then. Stoke had disputed Erik Pieters' foul on Eto'o just before the half-hour mark but they were helpless once Oscar dispatched a free-kick which curled viciously towards the post Begovic was guarding but still well beyond his despairing dive. It was the inside of the side-netting that bulged.

"It's a bit of a contradiction because we played so well but only won with a free-kick," said Mourinho. "Usually you win by scoring amazing goals in free play, and we had some fantastic play and very good collective movement out there. But the free-kick makes us happy because he trains for that. It's good to see a player who dedicates minutes every day after training on a specific thing score a beautiful goal like that." This was a seventh consecutive win in all competitions. The Etihad stadium awaits in the fifth round.

Man of the match Eden Hazard (Chelsea)