For a while it seemed as if Rafael Benítez's players feared Middlesbrough's home was armed with hidden tripwires destined to leave them lying flat on their faces.

Eventually, though, an initially tentative Chelsea had the measure of Tony Mowbray's impressive team, booking an FA Cup quarter-final against Manchester United at Old Trafford as it became clear that the only genuine Hazard on the pitch was their very own Eden.

Hazard, an influential second–half substitute – who says Benítez cannot do anything right? – helped create the second goal for Victor Moses after Ramires fired a half-volley beyond Jason Steele via Fernando Torres's shoulder.

They played highlights of Middlesbrough's 3-0 Premier League win over José Mourinho's Chelsea from 2006 throughout the stadium concourses before kick‑off and Boro's hopes of repeating that feat in an FA Cup context were bolstered by the visitors' team-sheet. Nathan Ake made his first start for the visitors, Paulo Ferreira began a game for the first time this season and Yossi Benayoun started his first match in blue since May 2011.

With Demba Ba on the bench, Fernando Torres was deployed as Chelsea's lone striker and George Friend, Boro's left-back, would have presumably been quick to dispute suggestions that the Spaniard has lost his speed. Creditably, despite being out-paced by the Spaniard on several occasions Friend, a £100,000 signing from Doncaster last summer, seemed well up for the challenge, making one splendid sliding tackle on the £50m forward which may have prevented a goal.

André Bikey did even better to block Oscar's shot following Victor Moses's cross but with Bikey and his fellow centre-half Stephen McManus taking turns to thwart Torres, Chelsea's early monopoly of possession was unproductive.

The promising Ake began well with Ramires, comfortably controlling midfield, but Mowbray's players began condensing the space around them, curbing that deep-lying pair's room for manoeuvre.

Even more encouragingly from the Boro manager's viewpoint his players were beginning to break slickly, with one such counterattack concluding with Scott McDonald meeting Nicky Bailey's cross before directing a header a yard wide. Benítez cannot have been overjoyed to see McDonald lose Ferreira with consummate ease.

Soon afterwards Bikey hobbled off, perhaps injuring himself with a kick aimed at Torres's bottom, but Seb Hines's introduction failed to interrupt Boro's improvement. Or Chelsea's temporary regression.

Mowbray's team might have taken the lead when Mustapha Carayol deceived Ferreira courtesy of a nifty switch of feet before unleashing a venomous shot from the edge of the area which Petr Cech could only parry. Happily for Chelsea, John Terry was on hand to clear the rebound before any home player could pounce.

Not only had Boro enjoyed the better openings but, amazingly, Steele was not required to make a significant save throughout the entire first half. Almost imperceptibly players such as Rhys Williams, Grant Leadbitter and Faris Haroun had relaxed into a passing groove sufficiently incisive to possibly prompt the odd Chelsea counterpart to remember their names. "We had a go," said a sanguine Mowbray. "For 50 minutes we had the better chances."

Few neutrals would have believed that Boro had lost seven of their previous nine Championship games, winning only one during a dismal sequences which threatens their promotion hopes.

Mowbray's team tend to struggle during Jonathan Woodgate's regular injury induced absences but despite being without their key defender and best player, here they looked reasonably assured.

Or at least they did until the 51st minute when Oscar crossed and after finding his path to goal blocked, Benayoun nudged the ball back to Ramires. The midfielder's half volley from the edge of the area was helped on its journey into the back of the net by a deflection off Torres. "I think Fernando was trying to get out of the way," said Mowbray, clearly a subscriber to the school that Torres should not claim it as only a second goal in his past 16 games. More significantly, Benítez's players had regained control and Hazard, on in place of Benayoun, curled a shot about a foot wide.

His introduction was to prove inspired, unsettling Boro's previous composure. He helped created his side's second goal by playing a one-two with Oscar culminating in a feint and square pass to Moses, who shot Chelsea into the sixth round.

Any creative tensions between Benítez and his players would fade into insignificance if the Spaniard comes face to face with Sir Alex Ferguson in the next round, but there is no guarantee the Spaniard will be there to do so now.