The first qualifying round brought shock defeats for Arsenal and Juventus.

"I think it is a bit strange - big teams going out in the pre-phase", Groenen told BBC Sport.

"I wonder if it's the right way to go."

Only holders Barcelona, plus Lyon, Bayern Munich and Women's Super League champions Chelsea have already automatically qualified for the group stage, which starts in November.

The second round of qualifying - played over two legs - will determine the 12 other teams to join them, with two-time winners Wolfsburg in the mix along with two-time runners-up PSG.

The 16-team group stage was introduced in the 2021-22 season, replacing the previous two-leg straight knockout format from the last 32 onwards with groups used only in the qualifying rounds.

"Don't get me wrong, it's always nice to play big games and I think from all the draws we could have had Manchester United was the hardest one we could draw," Groenen said.

"On one hand I don't fully agree with the system, but on the other hand I'm excited to play a game with this magnitude and pressure."

Last season's Champions League semi-finalists Arsenal were knocked out in the first qualifying round by Paris FC, while last year Manchester City lost to Real Madrid in qualifying.

'A proper goodbye'

It's been more than a year since Groenen left Manchester United for PSG, and the Netherlands international is keen to say "a proper goodbye" when she returns to Leigh Sports Village on Tuesday night.

"When the draw came out, I knew it was going to fall that way," she said.

"I'm really excited to go back and see all my people there, see the fans and actually have a moment to say a proper goodbye."

Groenen became United women's first overseas signing when she joined ahead of the 2019-20 season - the club's first in the Women's Super League after earning promotion from the Championship.

"Everyone knows I loved it at Manchester United and it was a dream for me to play there as a fan of the club since I was a child," added Groenen, who made 60 appearances in three years with the club.

"It means a lot to me to be able to come back and to have a proper goodbye."

Manchester United will be playing their first ever match in European competition, but Groenen says her side will not underestimate the WSL runners-up.

"It's going to be two great games because it's two teams who are quite level and on the same idea of playing styles.

"I know the attacking qualities of Man Utd, I know the set-pieces, so of course we have been talking about it here and what we are going to do against it. I think it's going to be a match-up all over the field."