The duo have been sidelined since early in the season but made their comebacks for the reserves this week.
Club captain and long-serving midfielder O'Connor suffered an ankle injury in November and striker El Alagui has been out with a knee injury since October.
But both came through an hour of action on Monday afternoon, so boss Uwe Rosler must decide whether to take them to Bramall Lane or give them another reserve run-out first.
Defender Scott Barron (hip) and back-up goalkeeper Richard Lee (shoulder) have undergone operations and will be out for the rest of the season.
- Sports & Recreation