Arsenal need response and Celtic have it tough – Champions ...

The Champions League returns this week for the third round of fixtures in the revamped elite club competition.

Here, the PA news agency looks at the key talking points with five British sides in action.

After slipping to a 2-0 Premier League defeat at Bournemouth on Saturday, when defender William Saliba was shown a controversial red card in the first half to see their unbeaten start abruptly end, Arsenal have the chance to get themselves back on track against Shakhtar Donetsk at the Emirates Stadium on Tuesday night.

Mikel Arteta’s side have impressed in Europe so far, beating Paris St Germain in the last round of games.

Shakhtar, meanwhile, are yet to score in their two Champions League fixtures – but come to London on the back of successive wins in the Ukrainian Premier League.

Can Liverpool manager Arne Slot plot another Champions League win when his team head to Leipzig? (Peter Byrne/PA)

Liverpool head to Germany for Wednesday night’s match at RB Leipzig having returned to the top of the Premier League after beating Chelsea at Anfield on Sunday afternoon for a seventh straight win in all competitions.

Arne Slot’s men are one of seven teams with a 100 per cent Champions League record so far.

While Leipzig may have lost both European fixtures, against Atletico Madrid and Juventus, Marco Rose’s side continue to impress in the Bundesliga, sitting level on points with leaders Bayern Munich – and will have an extra day’s rest following their comfortable 2-0 win at Mainz.

Manchester City kept the pressure on their Premier League title rivals on Sunday – but only just. John Stones’ header deep into stoppage time sealed a 2-1 victory at Wolves, albeit through a controversial VAR decision to allow the goal to stand.

City boss Pep Guardiola admits his team are not used to having to leave it so late to win games – something which looks unlikely in their next fixture at home to Sparta Prague.

The Czechs – who came through qualifying, beating Shamrock Rovers along the way – have four points from their opening two Champions League group games, as do City.

However, anything other than a comprehensive home win at the Etihad Stadium would be a major surprise, whatever team Guardiola sends out.

Aston Villa manager Unai Emery, centre right, has seen his side win both of their Champions League games so far (David Davies/PA)

Aston Villa produced a memorable 1-0 win over Bayern Munich earlier this month to continue their positive start to life back among European football’s elite clubs.

Unai Emery’s well-drilled side came from behind to win 3-1 at Fulham on Saturday, which left them fourth – but now level on points with Arsenal.

The visit of Bologna on Tuesday night is likely to pose another stern test of Villa’s European credentials, the Italians having given Liverpool plenty of cause for concern before eventually losing 2-0 at Anfield.

While Celtic sit top of the Scottish Premiership after Saturday’s 2-2 draw with fellow unbeaten side Aberdeen, Brendan Rodgers knows his squad are still a work in progress as far as European ambitions go.

Having opened the new Champions League group schedule with a 5-1 home win over Slovan Bratislava, the Bhoys slumped to a 7-1 thrashing at Borussia Dortmund last time out.

Rodgers felt his side got “spooked” at Signal Iduna Park. Celtic will need to put that tough watch out of their minds on Wednesday night away to Atalanta, who have four points from two games.