Chelsea twice had to come from behind in a classic FA Cup tie but booked our place in the quarter-finals with two goals in the space of 10 second-half minutes.
Luton came out at the start of the game determined to cause a cup upset and they did their chances no harm when they took an unexpected lead just two minutes into the match, when defender Reece Burke headed in off the post from a corner.
It seemed like normal service would be resumed when Saul Niguez slotted in his first goal for Chelsea with a placed effort into the bottom corner from the edge of the box, but against the run of play the Blues found ourselves behind to our Championship opponents a second time, shortly before half time, when Harry Cornick beat our offside trap and got a finish past Kepa one-on-one.
Despite dominating the second half, the travelling Chelsea supporters were made to wait for us to get the goals and the result our possession had deserved, as following some attacking changes by Thomas Tuchel we dealt Luton a quick double blow.
First Ruben Loftus-Cheek lifted the ball over the Hatters' back line, allowing Timo Werner to spin his marker cleverly and roll a composed finish under the goalkeeper. Then, 10 minutes later, the same combination gave us the winner.
Loftus-Cheek, who had moved from the back three to midfield between our goals, played Werner into the right-hand channel, but this time the German squared the ball across goal, where Romelu Lukaku was poised to muscle his way to the front of the queue and slide the ball into the back of the net.
The first of nine changes by Thomas Tuchel was in goal, where Kepa Arrizabalaga came in for Edouard Mendy. In front of him, Antonio Rudiger was one of two players to retain their place from the Carabao Cup final, with fellow centre-back Malang Sarr joining him in defence, while the eye-catching switch saw Ruben Loftus-Cheek slotting into the centre-back.
Kenedy made his first appearance since returning from loan in January on the left flank, with Callum Hudson-Odoi returning on the right. That meant a completely fresh midfield pairing of Saul Niguez alongside the evening's captain Jorginho.
The second player to keep their place from the weekend was Mason Mount, with forwards Timo Werner and Romelu Lukaku both being introduced in the front three, after impressing from the bench at Wembley.
The game didn’t start in the best fashion for Chelsea, as we found ourselves going behind in the match’s first piece of goalmouth action.
It came following a scrappy opening, when a couple of loose passes from Hudson-Odoi and Mount, followed by a hopeful long-ball from Luton, resulted in a corner for the home team. That was when disaster struck for the Blues, as the set-piece was headed across goal by defender Reece Burke, bouncing in off the inside of the back post, giving Kepa no chance as we went behind just two minutes in.
Cheered on by their fans, sat right on the touchline in a tight Kenilworth Road, the Hatters continued to make a bright start, finding space down the left, but Kepa wasn’t troubled again in the first 10 minutes.
At that point, there was a lengthy pause in play after Luton goalkeeper Jed Steer went down under no challenge when coming off his line to collect a cross ahead of Lukaku. It appeared to be a serious ankle injury as he left the field on a stretcher, with a word of consolation from Kepa, to be replaced by substitute Harry Isted.
The break in play seemed to dampen the atmosphere down a bit and helped Chelsea to settle in our unfamiliar surroundings, while new goalkeeper Isted looked a little hesitant when coming to claim a bouncing ball under slight pressure from Werner.
Getting our bearings
It took just over 20 minutes for our first real chance of the game to arrive. Following a loose pass at the back from Luton, Mount took possession and spread play to the right for Hudson-Odoi to cross, but Saul’s back-post header was comfortable for Steer to gather.
Lukaku then had a shot charged down on the edge of the box as the Blues started to gather a bit of momentum, and before long we made it count with an equaliser.
A quick attack starting with Kepa, after another dangerous Luton corner, gave Werner the chance to open up his stride and run at the home defenders, cutting across the edge of the box from the right.
The German stumbled as he went past the second man, but Saul was charging in to take over and place a perfect first-time shot into the bottom corner with his less-favoured right foot. That meant our No17 had scored his first goal for the club on his 17th appearance for the Blues.
With the scores back level, Chelsea were firmly in the ascendancy that many had expected from the start against our Championship opposition. That resulted in further chances too, as Saul was disappointed not to get his second Chelsea goal when breaking free inside the box, but Isted managed to save with his feet at the near post. Soon afterwards, Isted produced an even better save to tip a powerful Kenedy drive around the post.
There were still clear signs of the Luton goalkeeper’s inexperience, though, as the home team hung on for a spell. One misjudgement almost gave Lukaku a great chance when the stopper came for, but failed to reach, a bouncing ball on the edge of the box, but the defenders just about managed to clear before our striker could take advantage.
Back where we started
However, before the break Chelsea found ourselves behind again, completely against the run of play. With the Blues pushing numbers forward looking to go in for half-time with the lead, we were hit on the counter as striker Harry Cornick broke our offside line and with time to pick his spot was able to roll a finish past Kepa.
We tried to push back straight away, and hearts were in mouths when a Rudiger shot from range deflected off Lukaku’s back and floated towards goal with the keeper helpless, but it dropped just the wrong side of the crossbar and the Blues weren’t able to carve out any further chances before the break.
The second half began with a prolonged spell of Chelsea pressure, as we maintained possession around the final third and recovered it after a series of crosses from both flanks were cleared, but it was Saul again who went closest to a Chelsea goal early in the second half. His long-range effort had the power, but was too close to Isted to beat the goalkeeper.
Loftus-Cheek was starting to have an increasing influence on the game, striding out of his new defensive position and through midfield on the ball to launch attacks, and it was telling of the way momentum was shifting that when, 10 minutes into the second half, all 11 Luton players retreated into their own penalty area to defend a corner.
However, despite our possession, we were finding chances difficult to come by. In an effort to fix that, Tuchel made a double substitution, bringing off both wing-backs. In their place, Christian Pulisic was introduced on the right, while Saul moved out to the left and Mount dropped into midfield as teenager Harvey Vale joined the attack.
Chelsea hit back
When our second equaliser arrived, it came via a player who had been on since the start, though. Werner was the man to get it and he showed clever movement to roll his marker and get in behind the Luton defence in the box following Loftus-Cheek's perfectly judged pass. The German striker took his time to get the ball under control on the spin before a rolling a finish past the keeper and into the corner of the net.
With the scores level for the third time in the match, it was turning into a real old-school classic FA Cup tie, even if the balance of possession was now emphatically with Chelsea, along with Loftus-Cheek’s charges forward continuing to open up space for the Blues.
Werner was starting to find more and more room in the channels as the game went on, and it was via that route that the Blues took the lead in the game for the first time. A patient bit of play out on the right ended with Loftus-Cheek releasing Timo inside the box again and when he cut a low ball across the six-yard box from the byline, Lukaku used his power to get ahead of the defenders and slide us ahead from close range.
With around 10 minutes remaining, a lead to our name and our opponents starting to look tired, the space to play was finally emerging and we made good use of it, stroking the ball around in the kind of prolonged and confident spells of possession the Blues usually demonstrate in the Premier League and Champions League.
That made it almost impossible for Luton to rally and mount a late push for the equaliser that would take the game to extra time, managing only the occasional and increasingly desperate venture into our half. As a result, we were able see out the match in relative comfort with a game of keep-ball, as we secured our spot in the draw for the FA Cup quarter-finals.
We are back in Premier League action at the weekend, when we will face Burnley at Turf Moor at 3pm on Saturday.
Chelsea (3-4-3): Kepa; Rudiger, Loftus-Cheek, Sarr; Hudson-Odoi (Vale 63), Jorginho (c) (James 76), Saul, Kenedy (Pulisic 63); Mount, Lukaku, WernerUnused subs: Mendy, Williams, Hall, Kante, Kovacic, BarkleyScorer: Saul 27, Werner 68, Lukaku 78
Luton Town (3-5-2): Steer (Isted 14); Burke, Lockyer, Potts (c); Kioso, Berry (Campbell 63), Osho, Mendes Gomes (Hylton 76), Bell; Cornick (Jerome 63), Muskwe (Snodgrass 76)Unused subs: Bree, Naismith, Thorpe, ClarkScorer: Burke 2, Cornick 40
Referee: Peter Bankes