Howard was substituted from the game in the third term with a knee injury, forced to watch a tense final quarter from the bench.
The Saints have since confirmed that Howard required surgery to repair a medial meniscal tear, which the defender underwent on Tuesday.
The 26-year-old is facing a period of 3-4 weeks on the sidelines, but should be back in time for a potential Saints finals campaign, should Brett Ratten's men make it.
Hunter Clark has also undergone facial surgery after a heavy clash with teammate Dan Butler during the final term of the 15-point win. Clark was taken from the ground on a stretcher and the club confirmed the young gun suffered a compound fracture of the nose.
With his surgery complete, St Kilda expects the 23-year-old to be sidelined for two weeks.
Elsewhere at the Saints, rookie Jack Hayes is back running after suffering an ACL injury earlier in the season, with his rehabilitation continuing.
Looking ahead to this weekend's clash against Fremantle, the Saints expect both Rowan Marshall and Dan Butler to feature in the Saturday night clash despite receiving medical treatment on the sidelines on Friday night.