West Ham are on the front foot but the home defence is sticking well to the task at hand. Plenty of head tennis going on too.

Warning signs are already flashing for Plymouth.

Joe Edwards' poor header falls nicely for Jorginho on the edge of the box but the Italian international sends his skimming volley just wide.

It is hectic and scruffy already. Every Harriers touch is being roared on.

The Aggborough pitch has that lovely brown-flecked potential to cut up and create problems. Classic FA Cup.

Chelsea nearly in inside the first minute, Hakim Ziyech clipping a dangerous ball into the area but Plymouth goalkeeper Michael Cooper is sharply off his line to nick it away from the end of Callum Hudson-Odoi's foot.

Under way at Aggborough. Under way at Stamford Bridge. Anyone fancy another shock?

Plymouth Argyle manager Steven Schumacher: "The fans make us proud every week. They follow us up and down the country. I hope they have a good time and that we can put on a performance they can be proud of.

"The players know what they're going to be up against. We just ask them to enjoy themselves. We still want to try and be us. We just want to give it our best shot."

Chelsea

Chelsea assistant manager Arno Michels on Thomas Tuchel's absence: "He cannot be here today because he got tested positive yesterday. We will see what will happen in the next days.

"He was fully in charge in the week and was even there yesterday during preparation for the game. We'll stay in touch with him during the game."

Aggborough boos the arrival of the West Ham team and then erupts for the Harriers lads. Top atmosphere.

Image source, BBC Sport

Lawro's prediction: 0-2

Kidderminster began their FA Cup campaign in September, in front of 687 people at Noose Park - home of Sporting Khalsa of the Northern Premier League, Midlands Division.

Five months and six wins later, they will now play Premier League opposition in front of hundreds of thousands of fans across the world. It's great to see because the money they have made can transform the club and the whole feel-good factor is what the FA Cup is all about.

Harriers have played West Ham in the FA Cup before, when they were top of what is now the National League in 1994, and the Premier League side scraped a 1-0 win in the fifth round.

This time? Well, I think Hammers boss David Moyes would have picked a strong team for this round anyway, regardless of the opposition or venue, because his side have lost two on the bounce in the league and they need to get a bit of their rhythm back.

He won't be taking any chances at Aggborough either, especially because there are no replays in this round and that adds to the jeopardy for the bigger clubs.

Mist's prediction: I think Kidderminster will score, but West Ham to edge it. 1-2

Find out how Lawro and Mist think the rest of the weekend's FA Cup fixtures will go

Image source, Rex Features

If you want to know what it is like at a non-league during the week in the build-up to a huge FA Cup tie you could do a lot worse than read our behind-the-scenes diary with Kidderminster boss Russell Penn.

Here is a small sample from Tuesday:

Now I know how Jurgen Klopp and Pep Guardiola must feel when they do the food shop.

Normally I am able to dash around my local Tesco without a care in the world, but not during FA Cup fourth round week.

I was still in my club training gear collecting the weekly groceries with my wife, Kylie, and children Harley and Lyelah on Monday afternoon when I noticed people pointing.

I could hear them talking about Kidderminster in the cup as we walked past the frozen peas. It was a surreal experience.

And if you'd like to read a bit more about the Harriers players going toe-to-toe with West Ham today, you can do so here.

Spotted: a tin-foil FA Cup at Kidderminster. Now it's an FA Cup Saturday.

West Ham won't underestimate Kidderminster Harriers when the two meet in the FA Cup fourth round on Saturday, says Michail Antonio.

"I feel like this is a good draw for us," he said on the Footballer's Football podcast.

"We're going to try to go as far as possible in the FA Cup. Obviously they got a good win in the last round and are doing well.

"As a team we're not going to go there and disrespect them in any way. We're going to go there and give it our all because they haven't got this far by accident.

"I'm getting back (from Jamaica), I'm not too sure whether I'll be playing or not but if I am I'll give it my all, if not I'll wish the boys good luck."

Listen to the Footballer's Football podcast on BBC Sounds

There are 6,000 Plymouth fans at Stamford Bridge. They are making noise. Lots of noise.

The FA Cup wouldn't be the FA Cup without a reference to Ronnie Radford...

Image source, Getty Images

Kidderminster are the lowest-ranked team left in the competition currently sit third in the National League North table, 112 places below the Hammers who occupy fifth in the top flight.

Kidderminster started their FA Cup journey in the second-qualifying round. The Harriers have beaten six teams to get to this stage – Sporting Khalsa, Ware, Bedfont Sports, Grimsby Town, Halifax Town and Reading.

This is going to shock you, but Micah Richards is getting a bit excited about this game on BBC One. Top man.

If Plymouth need any inspiration today, they need only think back to this...

Image source, Getty Images

Image source, Getty Images

Image source, Getty Images

If you need a refresher, here is our report on that fourth-round tie between Chelsea and Bradford, which saw the League One side come back from 2-0 down to win 4-2 over Jose Mourinho's team in 2015.