St Kilda failed to record a win in the opening three rounds, prompting coach Ross Lyon to question whether the club's golden era had ended without a long-awaited premiership.
The Saints broke through for their first victory of the season against an undermanned Brisbane Lions team at the Gabba last week.
The Crows posted a third straight loss in round five, going down to Carlton by six points at Etihad Stadium, but were lauded for their performance, which was significantly better than their disappointing second-half display against Port Adelaide the week before.
Adelaide will start a warm favourite at AAMI Stadium on Saturday night, but Jacobs said his side wouldn't underestimate the Saints.
"St Kilda is coming off a win and it appears like they're starting to get their momentum going now," he said on Thursday.
"I don't think they're vulnerable at all.
"It's definitely an important game for our season. It's not a must-win [game] yet, but at 1-3 … you don't want to go 1-4 heading to Melbourne again next week."
Young defender Phil Davis completed training on Thursday and is expected to be recalled after two weeks on the sidelines with a shoulder sprain.
Brad Symes is also available for selection, despite suffering a badly broken nose in the loss to Carlton.
Jacobs said it was likely Davis would return to try to shut down St Kilda skipper Nick Riewoldt on Saturday night.
"Phil's such an important part of our defence," he said.
"It's worked out perfectly with Phil coming in against St Kilda because of their talls down there with Nick Riewoldt, Rhys Stanley and Justin Koschitzke."
Katrina Gill covers Adelaide news for afl.com.au. Follow her on Twitter: @AFL_KatrinaGill
