Regular first five-eighth Marty McKenzie left the field in the first half of the 33-12 loss to North Harbour with a head knock.
He has been ruled out for the match against Canterbury in Christchurch tomorrow.
It means Scott Eade will start in the pivot role, while promising No10 Mitchell Taylor will make his debut from the bench.
But the real problems are in the tight five. Southland is down a couple of front rowers.
Ethan de Groot picked up a knee injury during the Ranfurly Shield loss to Otago and may miss the rest of the season, while Chris Apoua is out with a calf injury for at least a month.
Robust flanker Phil Halder picked up a concussion and is ruled out, while back up openside Taine Te Whata has a fracture in his wrist and is probably out for the season.
"It is not a crisis," coach Dave Hewett said.
"We have lost one prop for about five weeks and we don't know yet with Ethan de Groot.
"He has dislocated his knee cap but we don't know what the upshot is."
Southland called in prop Howard Sililoto last week and is seeking another temporary replacement who may become permanent, depending on de Groot's knee.
McKenzie failed a head injury assessment earlier this week but "is feeling much better now".
"But we've decided it is best not to risk him if he is not 100 percent."
Southland's focus this week has been on cutting errors. Hewett felt the win was possible against North Harbour, but his side blew scoring opportunities and the chance slipped away.
Southland v Canterbury
Chch, tomorrow, 2.35pm.
Southland: Josh Moorby, Lewis Ormond, Javaan Fa’amoe-Ioane, Ray Nu’u, Lausii Taliauli, Scott Eade, Jay Renton, Bill Fukofuka, Matt James, Charles Alaimalo, Raymond Tatafu, Ben Fotheringham, Morgan Mitchell, Flynn Thomas, Joe Walsh. Reserves: Greg Pleasants-Tate, Shaun Stodart, Howard Sililoto, Mike McKee, Viliami Tosi, Logan Crowley, Mitchell Taylor, Moses Faletolu.