Right on cue... Messi drops deep to orchestrate Barca. He plays the ball out wide to the left, where Junior Firpo whips in a low cross.

Frenkie de Jong times his run perfectly, sliding past the keeper... but not the bar.

The ball comes back off the woodwork and the hosts hack clear.

This is the first time we've seen Messi since he saw red - figuratively and literally - in the Spanish Super Cup final against Athletic.

Not too involved so far, is the Argentine.

Now then. Rayo have a corner. Send the big lads up! Unfortunately they can't get anywhere near it. Tenacious defending by Riqui Puig averts the danger for the Catalans.

Barcelona have a cracking record here, by the way. Since losing at Vallecas in 2002, they have won the past 13 meetings in Madrid since.

Plenty of perspiration. Not much inspiration at the moment.

Rayo almost punished further.

Lionel Messi swings in the free-kick, Ronald Araujo tries to get a flick, but home keeper Stole Dimitrievski keeps his eye on the ball and claws away to safety.

You can't do that... Santi Comesana can't wait until full-time to get hold of Lionel Messi's shirt. The Rayo midfielder has a fistful of Barca cotton but only receives a yellow card for his trouble.

Free-kick in the home half, close to the right touchline...

Ooooh! Risky. Rayo defender Catena dives in on Barca winger Trincao, seeming to get more of his opponent's ankle than the ball. The ref disagrees and waves the Portuguese player to his feet.

Talking of kits... Rayo's Peru-esque colours are a personal fave. Decent spell of possession for the home side, but they can't find a way through.

Anyone remember those chew bars called Bruisers? That's what the Barca kit looks like.

Pink tops with black shorts and green socks. The visitors are chomping at the bit, actually. Started on the front foot and hogging possession.

Rayo probe in the Barca half for the first time, a wayward shot clatters the fence separating the pitch from the estate behind it.

Injury concern for Barca right-back Oscar Minguela, too. He grimaces but is fine.

Early chance for Barca! Junior Firpo and Antoine Griezmann combine down the left, the ball comes into the danger-zone, but Rayo scuff clear to safety.

Quick tot up of heads... 22? Yes. Toot! We're off.

A minute's silence before we kick-off, thought to be for a prominent Rayo fan who has died.

The touchline stand opposite the camera, by the way, has a long, bold banner stretched across the white seats with a message saying 'We will never forget them'. A tribute to those who have died in the pandemic.

Is there a sight more frightening for opposition defenders than Lionel Messi looking focused and stripping off his training top? Gulp.

Eerily quiet in Vallecas as the two sets of players jostle for elbow room in the tight tunnel.

Usually a cracking atmosphere there. Raucous set of fans, bit dilapidated, three sides with some high-rise flats at one end.

Recommend it when, well, you know. One day...

One team has already stuck their name in the quarter-final pot tonight. That's Sevilla.

Julen Lopetegui's side eased past Valencia in a 3-0 win, which finished a few moments ago at Estadio Ramón Sánchez Pizjuán.

Sevilla join Levante, Villarreal and Real Betis, who all won their ties on Tuesday.

Barca is a club which demands trophies and the Copa del Rey looks to be their best shout of winning one this season.

The Catalan club are 10 points adrift of La Liga leaders Atletico and aren't considered among the favourites for the Champions League - especially as they face French champions Paris St-Germain in the last 16.

"We want to fight to win every competition, but being realistic and looking at Atletico's advantage in the league and the form they're in, it's going to be very difficult," says Barca boss Ronald Koeman.

"As long as the league is possible we'll keep trying. The Copa del Rey is shorter, there are fewer games and we are in it to win it and that's what I want to see my team do."

Image source, EPA

Barca boss Ronald Koeman rings the changes - seven, in fact - from the weekend's league win at Elche.

But the spine of the side is a strong one.

Skipper Lionel Messi returns as expected from a two-match ban, with Sergio Busquets, Antoine Griezmann, Frenkie de Jong and Clement Lenglet also starting.

What about the hosts? Rayo boss Andoni Iraola has freshened up his side too. Looks like a defence-minded 4-5-1.

Anyone among you who is not a Rayo aficionado (suspect a fair few) will probably struggle to recognise many names in their starting XI.

However, former Brighton forward Leonardo Ulloa sits on the bench. Joining him there is ex-Watford midfielder Mario Suarez and striker Bebe - who Sir Alex Ferguson famously signed for Manchester United without seeing play.