Ferris was introduced after 60 minutes during Ulster's win against the Scarlets on Friday night - he last played in an Ulster shirt against Edinburgh in the PRO12 on November 2 2012 when he made his 102nd appearance.
In spite of the injury, Ulster and the IRFU have kept faith in the powerful specialist blindside loose forward by offering him consecutive contract extensions as he aimed to prove his fitness.
Ulster coach Mark Anscombe said: "He is huge and a big part of Ulster. To see him after all the hard work he's been through.
"The crowd love him. Hopefully the ankle pulls up well tomorrow."