Porto will have one last chance at goal as Christensen trips Diaz down Porto's left. Vieira sends the free-kick but Mbemba's caught offside. That's all, folks!
FULL-TIME: PORTO 0-2 CHELSEA
90' +2
Emerson enters the game and replaces M. Kovačić.
Chelsea make a late substitution. Emerson comes on to replace Kovacic.
90'
There'll be three more minutes of this.
88'
Porto understandably look a bit deflated. They've huffed and puffed all game but have little to show for it. Chelsea have managed their opponents perfectly.
85'
B. Chilwell has scored a goal for Chelsea!
GOAL! PORTO 0-2 CHELSEA! Chelsea get their second goal and it's Chilwell's first in the Champions League! The England left-back nips in from the left as Corona miscontrols the ball, deftly beats the closing Marchesin and taps into an empty net.
84'
Pulisic hits the post! Kovacic sends the American through on goal and he hits the right post from the right of the box. A second Chelsea goal really would put them in a strong position.
83'
Fábio Vieira enters the game and replaces Otávio.
Francisco Conceição enters the game and replaces Wilson Manafá.
Toni Martínez enters the game and replaces M. Marega.
Otavio is next to go off. The Portuguese U21 midfielder Vieira is on for him.
Last off is the hard-working Marega. On comes the Spanish forward Martinez.
First to go off for Porto is Manafa. On comes the 18-year-old forward Francisco Conceicao.
82'
Porto are preparing three substitutions. Mbemba successfully stops Kante as the Frenchman approaches the box.
80'
Thiago Silva enters the game and replaces R. James.
N. Kanté enters the game and replaces M. Mount.
Chelsea's own veteran centre-back Silva also comes on to replace James. Azpilicueta will move to right wing-back.
Meanwhile Chelsea get to make those changes. Kante comes on for their goalscorer Mount.
79'
M. Grujić gets yellow.
Grujic gets shown the yellow card for that foul on Pulisic. It's an easy decision by the referee.
Grujic completely takes Pulisic out as the American darts inside to set Chelsea on the counter.
Minute
Description
77'
Chelsea are about to bring on two more defensive reinforcements in the form of Silva and Kante. Azpilicueta nicks the ball off Marega just as the Malian looks to get a shot away.
75'
Chelsea have marshalled this game excellently. Even though Porto are growing in intensity, there isn't the sense yet that the hosts will be able to punish them.
73'
Christensen scrambles the ball out for a Porto throw as Porto come on the attack again. Conceicao gets shown a yellow card by the referee for trying to help his team restart too quickly.
71'
Marega goes down in the Chelsea box under a challenge from Azpilicueta. The referee instantly signals no penalty. It's a push from the Chelsea captain but not enough to warrant Marega's reaction.
70'
Porto get a free-kick down their left as Azpilicueta scythes down Sanusi. Otavio's delivery is cleared by James.
68'
Marega gets a shot away that sends Mendy diving low to his right-hand side. The Chelsea keeper has it covered.
65'
O. Giroud enters the game and replaces K. Havertz.
C. Pulišić enters the game and replaces T. Werner.
Giroud comes on to offer Chelsea a more traditional option up front. He replaces Havertz.
Here are those Chelsea substitutions. Pulisic replaces the luckless Werner first. The German's bound to find his form sooner or later.
64'
James' ball in from the free-kick is a promising one but Azpilicueta is unable to test Marchesin. Chelsea are about to make a few changes.
63'
C. Mbemba gets yellow.
Mbemba's booked for that challenge on Chilwell. It's been a fairly clean game, truth be told.
62'
Chelsea earn a corner off Mbemba and Chilwell tempts the defender into fouling him down the left.
58'
Otavio wins a free-kick in his own half as he's fouled by Chilwell. Chelsea still have this game under control for the most part.
55'
Diaz tempts James into a challenge with some stepovers and James obliges, poking out for a Porto corner. Porto force the ball into the net after Mendy saves Pepe's header but the whistle's already been blown for offside against Mbemba.
54'
Christensen finds James with his familiar diagonal ball and James plays it off Pepe for a Chelsea corner. James fires the corner in and Marega's the player to get the header away.
53'
Azpilicueta anticipates Diaz's run and uses his strength to muscle Diaz off the ball in the box. Diaz wants a penalty but it's an excellent challenge by the Chelsea captain.
52'
Chelsea see out the corner but Porto still have possession. The hosts are starting to look more threatening.
50'
Otavio looks for Corona wide right and finds him. The Mexican sneaks the ball through the legs of Chilwell and tries to burst into the box but finds his path impeded. A free-kick is not forthcoming.
48'
Rudiger fires a pass out wide to James who bustles his way inside. The wing-back brings down Sanusi while doing so and ends up giving away a foul. Tuchel shakes his head in the dugout.
46'
Chelsea start the half brightly. Werner heads over from Mount's cross after a flowing move by the visitors.
45'
Uribe performs a smart turn and holds off Jorginho to get a shot away from the edge of the box. It's a Porto corner. Grujic heads down Otavio's delivery and it's straight into the hands of Mendy. That'll be that for now.
HALF-TIME: PORTO 0-1 CHELSEA
We're underway again for the second half. No changes by either side at half-time.
44'
Porto continue to look for an equaliser before half-time. Azpilicueta thumps Otavio's cross away.
42'
Otavio floats in the free-kick which Mount heads out. Corona drives it back in and Azpilicueta sticks a leg out to divert it out for a corner. Mendy might just have had the shot covered.
41'
Porto are keeping Chelsea camped in their defensive third for now. Havertz steams in on Otavio and catches the winger's trailing leg to hand Porto a free-kick in a central position.
40'
Chelsea will be pleased with how they saw out that spell of Porto pressure earlier. Chilwell appeals for a free-kick after a push from Marega but nothing is given.
38'
Mbemba finds Sanusi with a good ball out wide but unfortunately for Porto Sanusi is offside.
36'
Porto look to recover quickly. Corona's caught offside from Pepe's throughball.
32'
M. Mount has scored a goal for Chelsea! Assist by Jorginho.
Jorginho swings in a searching ball from deep and Havertz keeps it alive. It works out well for Chelsea...
GOAL! PORTO 0-1 CHELSEA! That's a lovely goal from Mount. The England man turns Mbemba to reach Jorginho's pass and fires first-time for the bottom left corner. It beats Marchesin and hits the back of the net.
Jorginho's vision there was great but Mount's take of the pass was simply wonderful. He's a key man for Chelsea and for England at the moment.
31'
James fires in a cross from the right and Pepe makes the clearance. Porto are almost playing with a six-man defence. It's proving hard for Chelsea to break down.
30'
James finds himself out of position but recovers quickly to intercept Sanusi. The wing-back has been heavily involved for Chelsea in this opening half hour.
28'
Porto go on the attack again and Chilwell has to position himself well to put a stop to Otavio's run into the box. Porto get another corner but they're penalised for a foul in the area.
26'
Pepe thumps the ball forward to precisely no one. The former Madrid man is a veteran of the game and he's understandably disappointed with that. Up the other end, the offside flag goes up against Werner who tries to latch onto James' ball behind.
24'
Chelsea finally manage to break upfield. Mbemba blocks Havertz' pass and now it's Chelsea's turn to test Porto from a corner. Grujic heads away James' effort and Kovacic cuts out Diaz's counter-attacking run.
22'
The corner comes in towards Pepe but Kovacic does enough to hook it away. The ball comes off James for another Porto corner. The Portuguese champions have had a good start to this game.
20'
Jorginho arrives late on Diaz and Porto have a free-kick from the left. Pepe ventures forward for it. Otavio sends it into the box and the last touch is a Chelsea one. Porto will have a corner.
18'
Chelsea chase down Uribe's shot from outside the box. Chelsea have had the bulk of possession but have yet to really threaten Porto so far.
16'
Mount spots James free in the penalty area and looks to loop the ball towards him from the left. Marchesin sees the pass coming and ventures out to claim it.
15'
Christensen pings a direct pass forward for James. It's a pass the Dane has tried a few times already. It's unsuccessful this time but it looks like an approach which might bring Chelsea joy.
14'
Porto put some silky passing together and Otavio looks for Sanusi on the overlap down the left. The Nigerian tries to volley the ball across goal but fluffs his lines and it bounces out of play.
11'
Corona twists and turns to the left of the Chelsea box and hangs up a cross towards the centre. It's easy pickings for Mendy but it's Porto's first attack of note in the game.
9'
Chelsea's right wing-back James has plenty of space to run into. Sanusi does well to block him off and shepherd the ball out for a goal-kick.
8'
Otavio earns a free-kick for Porto down their right as Chilwell brings him down. The resulting free-kick is a strange one as Porto choose not to send the ball into Chelsea's box.
7'
Chelsea take the corner short and the ball ends up straight with Porto's goalkeeper Marchesin. The away side - for the administrative purposes of this game, at least - are likely going to have to stay patient.
6'
Mount goes on the run down the right channel. Sanusi gets across to intercept and puts the ball out for Chelsea's first corner of the game.
5'
Porto are going to miss Oliveira and Taremi here, players who have scored plenty of goals for them this season. Chelsea continue their positive start with Mount winning a throw-in from the right.
3'
Chelsea start on the front foot, making the pitch as wide as they can early on. Havertz fizzes a cross across the face of goal from the left of the box but there's no one in Chelsea colours there to make the most of it.
1'
The Slovenian referee Slavko Vincic blows his whistle and Chelsea get this quarter-final tie underway!
d
Hello! Welcome to our live text commentary of this UEFA Champions League quarter-final first leg match between Porto and Chelsea at the Ramon Sanchez Pizjuan Stadium in Seville, Spain.
When the draw was made a few weeks ago no doubt Porto and Chelsea will have welcomed being paired against each other. There are no easy games at this stage of the Champions League, yet this does feel like a tie of two underdogs with a semi-final against Real Madrid or Liverpool awaiting the victors.
Porto have reached the Champions League quarter-finals just three times since winning the competition in 2003/04, going on to be eliminated each time, while this is Chelsea's first appearance here since 2013/14. Chelsea might be considered slight favourites but with both legs set to be played in Spain, it's all to play for here in Seville.
PORTO (4-4-2): Agustin Marchesin; Wilson Manafa, Chancel Mbemba, Pepe (c), Zaidu Sanusi; Corona, Marko Grujic, Mateus Uribe, Otavio; Moussa Marega, Luis Diaz.
SUBS: Toni Martinez, Romario Baro, Felipe Anderson, Mamadou Loum, Fabio Vieira, Evanilson, Francisco Conceicao, Claudio Ramos, Malang Sarr, Joao Mario, Diogo Leite, Nanu.
CHELSEA (3-4-3): Edouard Mendy; Cesar Azpilicueta (c), Andreas Christensen, Antonio Rudiger; Reece James, Jorginho, Mateo Kovacic, Ben Chilwell; Mason Mount, Kai Havertz, Timo Werner.
SUBS: Callum Hudson-Odoi, Emerson, Marcos Alonso, Christian Pulisic, N'Golo Kante, Kurt Zouma, Willy Caballero, Olivier Giroud, Hakim Ziyech, Tammy Abraham, Thiago Silva, Kepa Arrizabalaga.
The two teams are out on the pitch in Seville for the first of two legs on neutral territory. Porto are in their blue-and-white home kit. Chelsea are in their ember orange third kit.
Porto have an uphill task in the second leg when it comes to budging past this Chelsea side. Conceicao's side created chances but none of them were good enough to really worry Mendy. That'll be something they think about as they reflect on this defeat.
Both teams return to domestic action then before meeting here in Seville again in six days' time. Chelsea will be confident of progressing now but Porto have already shown that they don't give up that easily. That's all for now. Goodbye!
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