Jacobs, 19, trained with his teammates at Alberton on Friday but fell ill over the weekend and was diagnosed with the debilitating condition on Wednesday.
The skilful half-back/midfielder had completed all of the pre-season training since being drafted by the Power with pick No.16 in November's NAB AFL Draft and had been pencilled in for a round one AFL debut.
However, football manager Peter Rohde said it was unclear whether the Sandringham Dragons junior would be fit to play in the season opener against Collingwood.
"Ben will have some more tests next week to try and determine how long he'll be out for," Rohde said on Wednesday.
"He trained last week no problems, so it’s come on suddenly and it’s very disappointing for the lad because he’s handled the pre-season as well as any first-year player we’ve seen in a long time.
"Unfortunately he’s going to be out for a few weeks now."
Jacobs will join Hamish Hartlett (hamstring), David Rodan (knee), Travis Boak (appendix), Jacob Surjan (knee), Jay Schulz (hamstring), Andrew Moore (groin) and Jason Davenport (shoulder) on the sidelines for Port Adelaide’s NAB Cup opener against Adelaide and Melbourne at AAMI Stadium on February 11.
The Power will be able to select from a squad of 29 players to play in the two games and captain Dom Cassisi said he expected young players, including draftee Cam O’Shea and rookie Callum Hay, to be given an opportunity.
"The [the draftees] have all showed glimpses of being good players," Cassisi said.
"Cam O’Shea is an elite runner and he's very competitive. Aaron Young is also competitive and Ben Newton…once he gets his body right is going to be a real star as well."
Port Adelaide has 14 players on its list aged 20 years or under, meaning the club will have little choice but to blood a number of fresh faces this season.
The Power haven't played in finals since going down to Geelong in the 2007 Grand Final, but Cassisi said he expected his team to return to the eight this season- regardless of the profile of the squad.
"Our expectation this year is to play finals. Last year we were a couple of games short. We won 10 games and we want to improve on that. We're going to have to win 12 games to make the finals this season, but we expect nothing less," he said.
"There will still be guys, who are really young playing games of footy but we expect them to come into the side and fulfil their role defensively and offensively for us to get a good result.
"Providing we have a good run with injuries and have got as many senior players out there as possible we definitely expect to play finals."
