Hassell has been sidelined for three weeks with a left Achilles problem and last week expressed his disappointment when claiming the injury had initially been mis-diagnosed.
But Tykes physiotherapist Chris Burton said: "He has an area of tendiopathic change in his left Achilles tendon which has been and continues to be improving with conservative management.
"A specialist opinion was sought earlier this week which confirmed the already diagnosed tendiopathic changes and also an inflamed retro calcaneal (heel bone) bursa.
"The bursa has been treated accordingly and a second ultrasound scan has revealed the bursa is no longer inflamed and the area of tendiopathic change is resolving.
"His rehabilitation program continues and has not altered in any way. It is hoped Bobby Hassell will begin to increase his rehabilitation on Monday."