Goals from Tommy Conway and Riley McGree during the opening 45 minutes proved to be crucial, taking Boro two points clear of Coventry at the top after a sixth straight win.

Patrick Bamford gave Sheffield United hope with a goal midway through the second half, but their task was made more difficult when debutant Joe Rothwell was sent off 10 minutes from time and they could not find an equaliser.

Blades midfielder Gus Hamer saw an early curling effort pushed away by goalkeeper Sol Brynn before Middlesbrough took control, producing some incisive attacking moves to open up the home defence on a number of occasions.

Hayden Hackney slipped a good ball through to Conway on the left-hand side of the area and the striker will have been disappointed with his effort from a promising position, blazing his shot wide.

Adilson Malanda saw a header saved by Michael Cooper and Morgan Whittaker also put himself in goalscoring positions, heading straight at Cooper and then seeing his shot flash beyond the far post.

The breakthrough came in the 19th minute when Luke Ayling, Whittaker and McGree combined well to set up Conway, who produced a fine finish.

Hackney went close to putting Boro further ahead, firing inches wide of Cooper’s right-hand post before Bamford had a great chance to equalise, bringing the ball down from a superb Hamer pass and firing a fraction wide of the target.

Brynn came to Middlesbrough’s rescue with a superb save to keep out Hamer’s well-struck effort and Cooper did likewise for Sheffield United, getting down well to turn Whittaker’s shot wide.

The visitors went 2-0 up in the final minute of the half when Hackney’s drive struck Cooper’s right-hand post, the ball bounced up and McGree was quickest to react, heading the loose ball into the unguarded net.

As the home side looked for an early second-half goal to inspire a revival, an inviting ball across the face of goal from Callum O’Hare was just too far in front of the lurking Bamford.

Bamford did pull a goal back in the 73rd minute, controlling a great ball into the area from Hamer before beating Brynn from 12 yards.

Rothwell, who came on as a substitute at the start of the second half, was shown a red card in the 80th minute following a reckless challenge on Alan Browne and that all but ended any hopes of getting anything from the game.