Winger Oster came off the bench in Saturday's draw against Preston and will be hoping to have done enough to convince boss Sean O'Driscoll he is worthy of a start.
Midfielder Fortune did not feature against the Lilywhites but could be handed a start if O'Driscoll decides to shuffle the pack.
Striker Steve Brooker has been dealt another injury setback after being told he needs a hip operation not long after recovering from an ankle problem and will be out for eight to 12 weeks.
Defender James O'Connor is rated as doubtful due to a knee injury, while Dutch defender Jos van Nieuwstadt, still recovering from a recent hernia operation, also misses out.
Source: Team_Talk