Luton subs: Shea, Potts, Berry, Hylton, Lee, Moncur, Collins, LuaLua, Nombe.
Luton starting XI: Sluga, Bree, Lockyer, Rea, Bradley, Naismith, Mpanzu, Tunnicliffe, Dewsbury-Hall, Clark, Cornick.
Chelsea subs: Caballero, Azpilicueta, Rudiger, Chilwell, Jorginho, Kovacic, Havertz, Hudson-Odoi, Giroud.
Chelsea starting XI: Kepa, James, Christensen, Zouma, Emerson, Gilmour, Mount, Ziyech, Werner, Pulisic, Abraham.
Stat: Luton last defeated a Premier League side in the competition in 2012/13 when they beat Norwich in the fourth round.
Stat: Since our home defeat to Bayern Munich last February, Frank Lampard’s Chelsea have only lost two of their 20 matches at Stamford Bridge, winning 13 of them.
Stat: Luton's leading scorer with six league goals is 30-year-old Ireland forward James Collins.
Stat: In the Championship this season, only Watford have scored fewer league goals away from home than Luton's six (with 14 conceded).
Hello and welcome to today's live coverage of the FA Cup fourth round clash between Chelsea and Luton. Kickoff is at 12pm UK time from Stamford Bridge.
On a slippery pitch with some snow on it, Chelsea get the ball in-behind early on but Sluga comes racing off his line well for Luton.
We are underway at Stamford Bridge!
Chelsea are playing a 4-4-2 of sorts today with Werner just behind Abraham and Mount deeper in midfield. The 22 year old captains Chelsea today for the first time.
Kepa makes a poor pass and forces Emerson to clear hurriedly. Cornick takes a long throw for Luton but Chelsea defend it well.
Werner does well on the left to get past Lockyer and put a cross into the area but there is no Chelsea player there to tap home the pass.
Mount carries the ball well for Chelsea but when Emerson receives the ball on the left, his cross is straight into the arms of Sluga in the Luton goal.
Luton have a good period of pressure up their left and Naismith gets a cross into the box which Kepa can claim easily for Chelsea.
Ziyech plays a lovely through ball for Abraham but Sluga comes off his line in flash and makes a crucial clearance for Luton.
James sets up Mount to shoot but Bradley makes a good block inside the box for Luton. That's good defending by the centre back.
GOAL! ABRAHAM! Chelsea take a quick throw as Ziyech finds Werner running into space and the German's cross deflects to Abraham, who scuffs home the opening goal past Sluga. Chelsea 1-0 Luton.
Mount delivers the first corner of the game for Chelsea and Zouma gets their first but heads over the bar.
Chelsea attack well with Abraham dropping short and then running into space and looking for a cut-back but Sluga claims at the near post.
Christensen and Emerson give the ball away in their own half but Luton can't make use of having the ball into good areas.
Chelsea have had 82% of the ball in the match so far.
GOAL! ABRAHAM! Chelsea have a 2-0 lead as James floats a cross into the area and Abraham flicks past Sluga who was caught in no man's land. Chelsea 2-0 Luton.
Luton win their first corner as Bree slides to get to an overhit pass and wins a corner off Emerson.
Luton take the corner short and Dewsbury-Hall whips in a lovely left footed cross from the right but Cornick's heads wide from the on loan Leicester man's delivery. That's a half chance at best.
Chelsea attack well as Abraham drops deep, turns and finds Pulisic on the left. The American crosses low into the area but Lockyer clears well for Luton. The Wales international has been good so far.
Ziyech gets a corner into the box and Zouma tries to attack. He is now down with a knock to the ankle from his landing. He needs treatment and both sets of players get some instructions from the bench.
CHANCE! Chelsea attack well down the right, a cross comes into the area, Werner dummies and Pulisic has an opportunity as the back post which he hits straight at Sluga.
GOAL! CLARK! Luton attack down the right, Bree pulls the ball back and Clark sees his shot go straight through Kepa. Another howler from the Spanish goalkeeper. Chelsea 2-1 Luton.
Since Chelsea went 2-0 up, Luton have responded well with 41% of the possession and four shots to one for Chelsea.
Chelsea have a reasonable opening as Werner finds Pulisic on the left but the American wingers curls his shot over the bar from a good position.
Close! James gets a low cross into the box from the right and Abraham can only get his studs on the delivery with Lockyer in close attendance. That could have been the hattrick for the Chelsea number nine.
Ziyech takes a corner from the left but it's cleared easily. Mount usually takes set pieces and has had assists this season from corners... maybe he should take the ones from the left?
It's ping pong in the Luton box as Abraham, Ziyech and Mount all have chances to shoot but only the latter does and it's blocked away. Chelsea need to make use of the pressure being exerted here.
Mount does brilliantly on the right to twice twist and turn and fire a superb cross into the area but no Chelsea player is in the six yard box!
HALF TIME. Chelsea lead 2-1 after Abraham scored twice in the first 19 minutes but the hosts switched off and a Kepa howler gave Clark a goal in the 30th minute. All to play for in the second half. Join us in 15 minutes.
Mount gives away a foul. Dewsbury-Hall delivers and Cornick gets his head to the ball at the near post but it's straight into the arms of Kepa.
CHANCE! Emerson is found on the left after some flowing Chelsea football but Werner can't finish on the volley at the near post as he steers wide under pressure.
The fourth official indicates two minutes of additional time to be played.
Abraham again drops deep, turns and this time finds James on the right but Werner can't control his pass when it arrives at his feet.
The half time break was 20 minutes as Luton were five minutes late having had to walk from their changing room outside the main stadium!
Luton have made a half time change as Daniel Potts replaces Glen Rea. They will now switch to a back four.
The second half is underway.
CHANCE! Ziyech backheels to James and the fullback plays a perfect cross for Pulisic to shoot from eight yards but his shot is straight at Sluga. That should be 3-1 to Chelsea.
Ziyech takes a short corner, links with Mount and fires a perfect cross which flashes across goal which Abraham not quite able to get onto it.
Ziyech shows great feet on the right and pulls the ball back to Mount who strikes just over the crossbar for the home side.
Chelsea are getting closer and closer. Mount finds Pulisic inside the box and his shot deflects just wide of goal.
CHANCE! Luton clear up the left and Potts gets onto the ball after a poor clearance by James. Mpanzu finds Cormick and his powerful shot draws an excellent save out of Kepa. That was so nearly 2-2!
Luton make a triple change as Luke Berry comes on to replace Ryan Tunnicliffe,
James Bree goes off for Kazanga Lualua and top scorer James Collins is on for Harry Cornick.
Dewsbury-Hall delivers a corner for Luton, Naismith heads down, Clark flicks on and Lockyer nearly converts before Kepa saves well. The offside flag had gone up though as Chelsea are let off.
Chelsea have lost some control of this match and could do with a calming player like Jorginho coming into the action perhaps.
Chelsea make their first change as Callum Hudson-Odoi replaces Pulisic.
Mount fires the ball into James, he fires into the feet of Werner and he German goes down. He wants a penalty for a tug on his arm but there simply isn't enough there.
CHANCE! Hudson-Odoi makes a lovely run and crosses perfectly into the box but Abraham heads a very good chance wide of goal. That really should have been his hattrick.
GOAL! ABRAHAM! Once again, Hudson-Odoi does some brilliant stuff as he plays a one two with Gilmour and squares for Abraham to tape home his hattrick! Chelsea 3-1 Luton.
Luton make a change as George Moncur comes on to replace Kal Naismith.
Chelsea make a double change as Olivier Giroud replaces Tammy Abraham and Kai Havertz comes on for Hakim Ziyech.
The home side are sitting off a bit now and allowing Luton to have the ball. It looks like Chelsea think it's job done now.
Luton have not given up and get a corner into the box and then a couple of crosses from the flank.
Chelsea make their fourth change as Mason Mount goes off and hands the captain's armband to his replacement Mateo Kovacic.
Clark is shown a yellow card for that foul inside the box on Werner.
PENALTY! Kovacic releases Werner and he is taken down by Clark. Clear spot kick.
MISSED! Werner takes the penalty and is denied by Sluga! The German just can't catch a break right now.
Hudson-Odoi releases Werner up the left but the German runs the ball out of play. That sums up his form right now.
FULL TIME. Chelsea win 3-1 as Abraham grabbed a hattrick. Luton gave a good account of themselves and kept it a 2-1 for 44 minutes where they still looked dangerous. Chelsea progress to the fifth round where they will play Barnsley. Chelsea 3-1 Luton. Thanks for joining us.
The fourth official indicates three minutes of additional time to be played.