Just as the hard-fought tie appeared to be heading into extra time, Gallagher, on as a second-half substitute, found space in the box to fire home and set up a last-eight clash with Leicester City next month.

The night had started badly for the Blues, who fell behind early on when Mateo Joseph put the visitors in front. We hit back through two expertly created goals from Nicolas Jackson and Mykhailo Mudryk, which gave us a lead at the interval.

However, Leeds continued to cause our backline problems and levelled when Joseph headed home at the back post just before the hour mark.

But as another 30 minutes loomed large, Enzo Fernandez broke forward, found Gallagher in the penalty area, and the Academy graduate finished coolly to send us into the quarter-finals.

A slow start

Pochettino made five changes to the Chelsea side that started the Carabao Cup final on Sunday: Robert Sanchez, Alfie Gilchrist, Trevoh Chalobah, Noni Madueke, and Mudryk all came into the XI.

Chelsea had looked to control the match from the opening moments but were caught out by Leeds, who took advantage of a mistake in our defensive third.

An attempted pass into the feet of Moises Caicedo from Axel Disasi was intercepted and Jaidon Anthony squared to Joseph, who composed himself and drilled a shot beyond Sanchez.

We did nearly find an instant response after good work down the left from Raheem Sterling created an opening for our captain for the night, Fernandez. However, the Argentine could only fire a low effort wide of Meslier's goal.

Drawing level

The Blues drew level following a lovely passage of play on the edge of the Leeds penalty area.

Jackson found Madueke, who laid the ball into the feet of Caicedo. The midfielder spotted Jackson had burst into the penalty area and fed the ball through to the striker, who slotted his shot through the legs Illan Meslier.

The goal kickstarted the Blues, who played at a higher tempo for the remainder of the first half. And the next significant save from Meslier came when Mudryk burst into the area at pace only to have his shot beaten away at the near post.

Blues take control

After dominating possession for much of the contest, the Blues got their noses in front in the 36th minute. A well-worked team move began with Caicedo working the space in midfield with the ball then switched to Malo Gusto.

The right-back moved it forward to Sterling, whose smart cut-back was finished off first time by Mudryk.

Leeds didn't wild, though, and a dangerous set-piece created a clear-cut chance for Dan James, only for the Whites' forward to fire over harmlessly into the stand.

Anthony also went close to levelling the tie following a powerful run down the channel, only to curl his effort narrowly wide of the post. That ensured we went into half-time we a lead intact.

Punished again

Despite Jackson and Madueke continuing to give visitors defence food for thought after the interval, Leeds kept themselves firmly in the mix in an open cup tie.

They landed the next punch of a see-saw contest when Anthony worked half a yard on the Chelsea left flank and his cross was perfectly timed for Joseph to head home his second of the night from close range.

Pochettino responded by immediately introducing Gallagher and Ben Chilwell from the bench, but Leeds defended well, save for one bright moment where Chilwell played in Mudryk, only for his touch to let him down at the crucial moment.

At the other end, Sanchez reacted quickly to produce a stop after Anthony's long-range effort took a nasty deflection.

Blues win it late

The lively Anthony again went close as the visitors searched for a winner, but his curled effort thankfully went high over Sanchez's crossbar. The Blues fashioned chances in return, with substitute Levi Colwill going close from a Chelsea corner.

The crucial moment finally arrived as the game entered the 90th minute. Enzo moved infield with the ball and scanned the pitch for a pass. He spotted Gallagher, who had darted into the penalty area, and punched the ball into the meet of the midfielder.

Gallagher collected the pass on the back foot, swivelled away from a covering defender, and then displayed composure to guide a shot beyond the onrushing Meslier.

There was just time for Pochettino to hand a Chelsea debut to Jimi Tauriainen before the referee's whistle sounded to book our spot in the quarter-finals and keep our dreams of claiming silverware this season very much alive.

What it means

The win ensures a quarter-final meeting with Leicester City, which will take place at Stamford Bridge over the weekend of Saturday, March 16.

What is next

Chelsea have less than 72 hours before returning to action for a Premier League trip down the road to neighbours Brentford. Kick-off on Saturday at the Gtech Community Stadium is 3pm.

The teams

Chelsea (4-2-3-1): Sanchez, Gilchrist (Colwill 74), Disasi, Chalobah, Gusto (Chilwell 61); Enzo (C), Caicedo; Mudryk (Tauriainen 93), Madueke (Gallagher 61), Sterling (Palmer 74); Jackson.

Unused subs: Petrovic, Samuels-Smith, Murray-Campbell, Harrison.

Scorers: Jackson 15, Mudryk 37, Gallagher 90.

Booked: Caicedo, Chalobah. Fernandez

Leeds United (4-2-3-1): Meslier, Roberts, Firpo, Rodon, Cooper (C); Ampadu , Gray; Anthony James (Gnonto 78), Piroe (Summerville 78); Joseph

Unused subs: Klaesson, van den Heuvel, Cresswell, Kamara, Bamford, , Shackleton, Byram.

Scorers: Joseph 8, 58

Booked: Firpo

Referee: David Coote

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