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Chelsea beat Chesterfield in round three, while Plymouth knocked out Birmingham
Tuchel tests positive for Covid and misses tie
Plymouth are seventh in League One
Chelsea are eight-team winners, last in 2017-18
Plymouth's best FA Cup run saw them reach the semi-finals in 1983-84
Kidderminster 1-0 West Ham
More good defending. Amari Morgan-Smith gets his head to the corner and clears it far enough for keeper Luke Simpson to charge out and gather.
Harriers haven't conceded now for over seven hours. Granted, they've not faced forwards of this calibre during that time. 30 minutes gone, though, and they've coped well.
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Daniel Godfrey: Middlesbrough last night, Plymouth leading after 8 mins and now Kidderminster. My team (Chelsea) haven’t gotten the start they wanted but I love this competition.
Kidderminster 1-0 West Ham
Superb defending from Matt Preston, who sticks his boot towards his own goal and clears a Ryan Fredericks cross over his own bar.
Chelsea 0-1 Plymouth
It's a "sackable offence" says Matt Upson as Mateo Kovacic fails to get his corner kick past the first Plymouth man at the near post.
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Kidderminster 1-0 West Ham
Just wide!
Omari Sterling-James gets his free-kick past the wall but also past the upright. West Ham survive.
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Unfortunately Lukaku doesn't seem to be working out for us. Not really sure what's happened to Havertz either, been on the bench but has hardly played for months. The curse of the Chelsea striker continues.
Will in London
Chelsea 0-1 Plymouth
Romelu Lukaku has not had a sniff so far.
That's a £97.5m striker.
Kidderminster 1-0 West Ham
Harriers have another free-kick near the Hammers box as Ashley Hemmings is knocked to the turf. We know where this is going. Issa Diop is having a bit of a shocker.
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Stan DeCwikiel Jr: Two days in a row, two second-choice keepers, two gaffes coming out of the box for no reason, two goals by the lower-league sides. Inquiries begun.
This right here is what the FA Cup is all about. It's had detractors in recent years, but nothing serves up pure football romance like this competition.
Chelsea 0-1 Plymouth
Antonio Rudiger is dangerous at set-pieces and the German shows signs of exactly why, nearly heading in Hakim Ziyech's corner.
Kidderminster 1-0 West Ham
The Kidderminster fans are currently chanting their review of the Hammers side. It's not complimentary.
Chelsea 0-1 Plymouth
Chelsea are looking back into the game but Callum Hudson-Odoi is being left frustrated so far.
James Wilson comes across and makes a strong challenge to barge the Blues man off the pitch.
It was right in front of the travelling Plymouth fans and they loved that.
Kidderminster 1-0 West Ham
Dion Dublin
Former Aston Villa striker on BBC Match of the Day
That is a very, very calm finish, Penny takes his time, does not rush or snatch at it and sidefoots it – no power needed. Areola needs be better and should have cleared it out.
Image source, gettKidderminster 1-0 West Ham
David Moyes frowns on. His team are rocking in the face of a National League North wave.
Kidderminster 1-0 West Ham
Well, if West Ham were uncomfortable before, they're rattling in their boots now.
Alex Penny
LIFT OFF!!!!
They do get it in the mixer, drawing Alphonse Areola out for a punch he fails to make. The ball drops for Alex Penny and he slots it in.
Aggborough erupts. The shock is on!
Penny puts Kidderminster ahead against West Ham
Chelsea 0-1 Plymouth
FA Cup: Macaulay Gillesphey heads Plymouth into shock lead at Chelsea
Chelsea 0-1 Plymouth
Chelsea are rattled.
Jorginho is the first man into the book as he drags down Luke Jephcott inside the centre circle.