It was far from plain sailing at Stamford Bridge, but Ben Chilwell’s effort deflected into his own net by Olivier Norwood in the 24th minute, and a clinical finish from sub Ziyech with seconds left, proved sufficient for us to progress.

We also kept a club record-equalling seventh consecutive clean sheet, although a bad David McGoldrick miss midway through the second half should have ended our run without conceding. He headed wide from six yards out, and Kepa also saved well on two occasions to blunt the Blades.

It had been more or less all Chelsea in the first hour of this quarter-final tie. After our goal, Christian Pulisic had chances to extend our advantage, one all his own making shortly after the restart.

Our slender advantage until late on gave the Blades hope, but Ziyech put the seal on another victory to send us safely through and make it 15 without defeat ahead of what promises to be a dramatic finish to the season after the international break.

The selection

There were nine changes to the Chelsea team, with Kurt Zouma and Mateo Kovacic the two to keep their place from Wednesday’s win. The Croatian made his 100th start in blue.

Kepa was in goal and Emerson formed part of the back three, as he did at Barnsley in the previous round. Andreas Christensen returned from illness and captain Mason Mount from suspension. Billy Gilmour anchored the midfield and Olivier Giroud featured for the first time this month.

As expected, Chelsea dominated possession in the opening stages, but only Kepa was called into action, saving comfortably from David McGoldrick and Phil Jagielka as the visitors tried to land the first blow.

Helping hand

The Blues stepped up a gear as the midway point of the half approached and Callum Hudson-Odoi forced a corner from which we took the lead. Mount’s delivery missed everyone in the box and reached Chilwell, hovering 25 yards from goal. He set himself before firing a cross-shot that Norwood deflected past the helpless Aaron Ramsdale.

We camped ourselves in Sheffield territory in search of a second that would likely kill the tie. On the half-hour, a lovely Gilmour pass picked out Hudson-Odoi, but the offside flag was up.

With the interval fast approaching and Chelsea in cruise control, a short Norwood pass was intercepted by the lively Pulisic. He briefly lost his footing before attempting to dink the ball over Ramsdale, who stood tall and blocked.

A piece of Pulisic genius lit up the start of the second half. He flip-flapped his way past two Blades, Ronaldinho-style, before shooting at Ramsdale. The rebound fell his way, too, but he couldn’t control his second effort.

Poor Pulisic was the principle target of plenty of physical challenges from the visitors, and one rake down the back of his calf left him in serious pain in front of the dugouts. Thankfully he was able to continue.

Sharper Blades

Shortly after the hour, Tuchel brought Cesar Azpilicueta and Reece James on for Christensen and Giroud. Mount led the line, with Hudson-Odoi moving forward.

The Blades were starting to offer more of a threat going forward and wasted a golden opportunity to equalise in the 67th minute. John Lundstram’s cross was ideal for McGoldrick, a scorer here in the league fixture, but he contrived to plant his header wide of the goal.

Kepa then had to dive to his right to parry Oli McBurnie’s bending shot to safety as the Blades sensed Chelsea fragility.

Tuchel responded by introducing Kai Havertz and Ziyech. Hudson-Odoi and Gilmour made way, with Mount reverting to midfield and Havertz heading up top.

Late drama at both ends

With 13 minutes remaining, Kepa stuck out a strong left hand to stop McGoldrick’s effort from a narrow angle going any further. Enda Stevens then headed wide. The whole momentum of the tie had shifted.

On came N’Golo Kante to help the stem the tide and it proved effective as we denied the visitors a sight of goal until the first minute of stoppage time. Ben Osborn’s cross was intercepted by Zouma but only as far as sub Rhian Brewster, whose strike took a tiny deflection and flew into the side-netting with Kepa beaten.

Just as on Wednesday, an injury-time breakaway led to a second Chelsea goal. Ziyech won a loose ball and found Kovacic, who moved it on to Chilwell. His pass back inside was superbly taken down by Ziyech, who had the finish to match on the slide.

Victory was ours and we have a Wembley date to look forward to next month!

What's next?

Most of the players will now head off on international duty. We return to action with a home league game against West Brom on Saturday 3 April. The FA Cup semi-finals are due to take place on 17/18 April. We will discover our opponents at half-time in the Leicester vs Man United game.

Chelsea (3-4-2-1): Kepa; Zouma, Christensen (Azpilicueta 63), Emerson; Hudson-Odoi (Havertz 72), Gilmour (Ziyech 72), Kovacic, Chilwell; Mount (c), Pulisic (Kante 83); Giroud (James 63).Unused subs Caballero, Rudiger, Alonso, Werner.Scorers: Norwood own goal 24, Ziyech 90+2

Sheffield United (3-5-2): Ramsdale; Baldock, Jagielka, Stevens; Bogle (Mousset 90), Lundstram, Norwood (Brewster 78), Fleck, Osborn; McGoldrick (c), McBurnie (Burke 75).Subs: Foderingham, Lowe, Bryan, Gordon, Brunt, Ndiaye.

Referee Andy Madley