Hartlett struggled with hamstring problems in 2009, managing just 11 of a possible 22 games in his debut season.
Power fitness coach Cam Falloon said the club would take a conservative approach to the prized No.4 draft pick’s rehabilitation.
"Hamish has done a standard hammy but it is different to the previous ones he has had," Falloon told Fox Sports.
"It will be a four-weeker, so he won't be around for the start of the NAB Cup, but could play at some stage. He has to go through the rehabilitation process and will have two months to get himself right for round one."
The injury caps off a nightmare pre-season for the 19-year-old, who was struck down with glandular fever before Christmas.
He was also on modified duties for much of last summer as he recovered from a shoulder reconstruction.
Port Adelaide had earmarked Hartlett for a greater midfield role this season in the absence of former vice-captain Shaun Burgoyne, retired onballer Peter Burgoyne and injured livewire David Rodan.
Hartlett is expected to be handed Shaun Burgoyne’s old No.8 guernsey when the jumpers are officially presented next month.
