The Edinburgh stalwart sustained an injury to his left calf muscle during the first half of Scotland's 56-10 victory against Portugal on Sunday.
It has been reported that the injury will keep Jacobsen sidelined for six to eight weeks ruling him out of Scotland's World Cup campaign. The 28 year old will have an uphill battle to return to fitness for Edinburgh's Heineken Cup opener at home to Toulouse on Saturday, 10 November.
Edinburgh fans will be wishing him a speedy recovery as Jacobsen has lined out 41 times for the Scottish capital in the Heineken Cup and featured in all six of their European games last season. The prop was also central to the team that made it through to the Heineken Cup quarter-finals in 2004.