The club confirmed on Tuesday that Johannisen will avoid surgery, as the tendon did not completely tear off the bone.
Johannisen injured his hamstring in the third quarter after kicking a long goal from outside 50 and sat out the remainder of the game.
The 23-year-old has been in career best form this season, averaging 24.5 disposals per game.
— AFL (@AFL) April 16, 2016
Meanwhile, exciting young Greater Western Sydney forward Jarrod Pickett has been ruled out for the rest of the season due to a foot injury.
Pickett, who was selected with pick No.4 in the 2014 National Draft, has suffered a lisfranc injury, the same injury which Collingwood star Dane Swan sustained in Round 1 this season.
“It’s an unfortunate injury for Jarrod who has been progressing really well,” GWS head of athletic performance David Joyce said.
“As is always the case with our players, Jarrod’s long-term welfare is the most important thing so we’ll put in place a rehabilitation program to ensure he returns stronger than ever.”