The 24-year-old injured the ligaments in his foot in his side's last home game, the 2-0 victory against Middlesbrough.
He missed Friday's defeat at Hull while Carlos Corberan and his staff awaited news from a specialist.
Normal protocol for the injury requires surgery and Albion, who welcome second-bottom Wigan tomorrow night, are waiting for a second opinion before confirming the procedure.
Corberan said: "In terms of the Diangana situation, it's going to take more time to fix his injury. Normally he is going to need surgery, we are waiting for another consultation for him.
"But normally it will be difficult we can watch him before the end of the season, if he has the surgery, very difficult."
Albion recalled under-21s forward Mo Faal, who turned 20 last month, from a loan at National League North outfit AFC Fylde.
Faal has been in electric form to help propel the Coasters towards the summit of the sixth tier with 10 goals in 16 appearances after earlier in the season struggling to make an impact in the same division at relegation-threatened AFC Telford United.
Faal will make up part of Albion's matchday squad against Wigan, likely alongside fellow academy youngster Jovan Malcolm. Malcolm and Rico Richards made up the substitutes at Hull.
The Baggies require youthful attacking cover due to the injury to Brandon Thomas-Asante, which while not as serious as Diangana's setback, still blunts Corberan's firepower.
Thomas-Asante is missing against the Latics but could feature against Huddersfield on Saturday. Tom Rogic is back in training and is pushing for a return to action.