An 18-team league phase -- in which all clubs play six matches, three at home and three away -- has replaced the former 16-team group stage as the women's competition comes more into alignment with the men's version.

The top four in the standings qualify directly for the quarter-finals, while the teams finishing fifth to 12th will advance to a knockout play-off round.

With such high stakes, teams need to hit the ground running.

Reigning champions Arsenal could hardly have asked for a more difficult start to the new-look competition as they host French Premiere Ligue winners Lyon at Meadow Park in a repeat of last season's semi-final.

Arsenal emerged victorious from that two-legged tie 5-3 on aggregate but come into this season's meeting on a poor run of form.

A 3-2 defeat at Women's Super League title rivals Manchester City on Saturday followed on from back-to-back draws against Manchester United and Aston Villa, leaving Renee Slegers's side fifth in the table.

The absence of injured captain Leah Williamson has exposed Arsenal's defensive frailties over their last three winless WSL outings.

"When we have momentum, capitalise, be ruthless and protect yourself really well for when the momentum shifts again," said Slegers after Saturday's defeat to Man City.

"I think that's definitely something we'll look at and that we want to do better. But heads up looking forward to Lyon.

"We're going to do everything we can to recover from this one and show up in a really good Arsenal way on Tuesday."

Lyon, meanwhile, are rampant and sit top of their domestic league with a perfect four victories from four with 19 goals scored in the process.

- Heady start under Giraldez -

Under new coach Jonatan Giraldez, the orchestrator of Barcelona's European dominance earlier in the 2020s, the early signs are that Lyon are going from strength to strength.

Ahead of their trip to Arsenal, they backed up a statement 6-1 win against last season's second-placed side Paris Saint-Germain by routing Lens 8-1 on Friday.

With an attack likely consisting of Kadidiatou Diani, Melchie Dumornay and Marie-Antoinette Katoto, as well as new star signing Jule Brand, the French side come into the clash with no shortage of high-quality forwards eager to get at Arsenal's backline.

Last season's runners-up Barcelona fell agonisingly short of winning a third consecutive Champions League in May but will be keen to put down a marker when they welcome German giants Bayern Munich also on Tuesday.

Many of the Barca squad will also be entering the Champions League this term with a score to settle following defeat in the showpiece match to Arsenal and a penalty shoot-out loss to England in the final of the Women's European Championship in July with Spain.

One such player is Aitana Bonmati.

Despite recently claiming a third consecutive Ballon d'Or, Bonmati will want to put last season behind her as she overcame a bout of viral meningitis in the summer, sandwiched between Champions League final defeat and missing a penalty in the shoot-out of the Euros decider.

After scoring five goals in Barca's first three Liga F matches, the 27-year-old has failed to find the net since early September.

Bayern, undefeated and second in the Frauen-Bundesliga, will offer her the perfect high-profile occasion to respond to her critics.

Elsewhere on matchday one, English champions Chelsea visit Dutch side Twente and PSG travel to two-time winners Wolfsburg of Germany -- both on Wednesday.

Real Madrid host Roma, while Man United take on Norway's Valerenga and Juventus welcome Benfica.