Inevitably, attention will now turn to what Walsh's injury could mean for Chelsea's home match against Arsenal.
Chief among the concerns is whether she will be fit to feature, with Chelsea sitting third in the Women's Super League, two points behind leaders Manchester City.
Asked by BBC Sport after the match, manager Sonia Bompastor said: "Yeah, so more we were trying to be cautious with her, she just felt a little bit of quad. Hopefully it's not too bad. We'll assess her tomorrow and see if she's available for Sunday's game. It's too soon to say now."
There is also a question mark over Lauren James, who is hopeful of a return, while captain Erin Cuthbert, Manaka Matsukubo and Aggie Beever-Jones remain sidelined through injury.
The performance against Vienna was another unconvincing display from Chelsea, particularly in attack, as they squandered chances to extend their lead.
As the game wore on, they also struggled to control the visitors despite starting as overwhelming favourites, no doubt affected by the loss of their key playmaker Walsh.
Although they could have extended their lead, they also gave away a lot of chances and could have ended up with less than the expected three points in what, on paper, looked their easiest fixture.
Bompastor cut a tense figure on the touchline as she attempted to guide her side to an opening victory in the league phase of Europe's premier club competition.
It is a tournament Chelsea have never won, despite Bompastor insisting they are capable of doing so, while also acknowledging this season could be a transitional one for the club.
Concerns remain that Chelsea, who have spoken about a lack of a clinical edge after two of their opening three Women's Super League matches, are still searching for their identity this season, particularly with Arsenal on the horizon.
That's not to mention a trip to Bompastor's former club Lyon, who won 8-0 in the Champions League on the same night, to follow next week.
After the match, there was an admission that were not at their best but had ultimately got the result they needed.
Bompastor added: "I put out a very experienced team. I think we could have controlled the game better and killed the opposition's hope by scoring again. Sometimes you have to focus on what is most important, which was winning the game.
"I think we have enough time to recover for the game at the weekend. I know we will have fresh legs and the game will be very different as it is a London derby."