Chelsea welcome Barcelona to Stamford Bridge on Tuesday night for the first leg of their Champions League round-of-16 tie.

Antonio Conte’s side have been under pressure of late while Ernesto Valverde’s Barca have lost just once since the Champions League group stages concluded in early December.

Here, Press Association Sport looks at some of the major talking points ahead of the heavyweight contest.

A welcome distraction

A 4-1 Premier League defeat at Watford was a low point in Chelsea's season so far
A 4-1 Premier League defeat at Watford was a low point in Chelsea’s season so far. (Adam Davy/PA)

Chelsea have won just four of their previous 12 matches across all competitions leading into this mammoth meeting.

Conte’s position has been under constant scrutiny as they were beaten by Bournemouth and Watford by an aggregate scoreline of 7-1.

Chelsea also lost to Arsenal in the semi-final of the Carabao Cup but warmed up for Barcelona with straightforward wins over Premier League bottom side West Brom and Championship strugglers Hull.

Tuesday will be a different proposition but will give the Chelsea players a chance to address their patchy form in the most emphatic of ways.

What shape will the Blues be in?

Danny Drinkwater could make his first Champions League start for Chelsea.
Danny Drinkwater could make his first Champions League start for Chelsea. (Adam Davy/PA)

Conte has switched between two formations for much of the campaign, sometimes sticking with the back three which helped Chelsea to the title last season, while also operating with a 4-3-3.

It is hard to see past a 3-5-2 formation as they look to stifle Barcelona’s creativity in the middle of the park.

With Tiemoue Bakayoko and David Luiz injured, the midfield trio almost picks itself with Danny Drinkwater and N’Golo Kante expected to start alongside former Barca man Cesc Fabregas.

Time for Lionel to end his Messi run in this fixture

Lionel Messi has never scored against Chelsea, missing a penalty when the sides met in 2012.
Lionel Messi has never scored against Chelsea, missing a penalty when the sides met in 2012. (Stephen Pond/EMPICS)

Lionel Messi, regarded as one of the greatest players in the history of the game, has an abysmal record against Chelsea.

The diminutive Argentinian forward has brushed aside all those who have come up against him in the past – apart from the Blues.

Messi is yet to score following eight previous encounters with Chelsea and he will want to put that right, starting at Stamford Bridge on Tuesday night.

Striking opposites

Regardless of formation, Conte has a decision to make at the very top of the pitch when it comes to which striker is selected.

January signing Olivier Giroud left Arsenal because he could not get a game but has impressed in his three outings so far and has been prepared to put in a shift – opening his account in the FA Cup win over Hull on Friday.

In stark contrast, summer recruit and club-record acquisition Alvaro Morata has been sidelined with a back injury in recent weeks after a spell of poor form which left Conte scouring Europe for another attacking option – it remains to be seen who will get the nod to lead the line on Tuesday.

Barca need to become record breakers

The likes of Luis Suarez (left) and Messi will hope to inspire Barcelona to a rare win over Chelsea
The likes of Luis Suarez (left) and Lionel Messi will hope to inspire Barcelona to a rare win over Chelsea.(John Walton/EMPICS)

As well as Messi’s inability to score against Chelsea, Barcelona on the whole have always found the Premier League side a challenge.

Chelsea have never lost to Barcelona when they have managed to keep 11 players on the pitch and their 2012 semi-final, which the Blues won on their way to a maiden Champions League trophy, is still a memory fans of the club cherish.

Barcelona may be touted as favourites for this tie given their LaLiga form but they will have to avoid history repeating to do so.