The 2012 champion was assured of its progression to the knockout stages a fortnight ago, despite losing 1-0 in Basel, but will need to secure three points this week to guarantee first place.
Steaua is already out of the competition and can no longer qualify for the Europa League after failing to record a single victory in five matches.
Jose Mourinho's men are currently one point clear of Basel at the top, but would drop to second if the two sides end the group level on points owing to the team's inferior head-to-head record.
Schalke, which was held to a goalless draw by Steaua last time out, is not yet out of the running. A win for the Bundesliga outfit against the Swiss champion - combined with a Chelsea defeat - would see the German side emerge as group winner.
Chelsea's last three Premier League games have been high-scoring affairs, producing a total of 16 goals.
The most recent of those was a 3-2 defeat at Stoke City on Saturday and Chelsea has now conceded three or more goals in back-to-back league games for the first time since Oct. 1999.
Chelsea, then, is showing some weakness at the back, and the club's record of 17 goals conceded in the Premier League this season is already two more than it let in during the whole of Mourinho's first campaign in charge in 2004-05.
Steaua, meanwhile, has gone 11 matches unbeaten in all competitions, but recorded six draws in that run and failed to win a single match in November.
Samuel Eto'o was fit enough to come off the bench at the weekend, but David Luiz (knee) and Oscar (ankle) both missed out and could remain doubtful for Chelsea's final group fixture. Andre Schurrle, who scored both of his side's goals on Saturday, could be missing with a calf problem, and Marco van Ginkel (knee) is a long-term absentee.
The Romanians will be without Alexandru Bourceanu, who is serving a one-game suspension, while Lucian Filip (broken leg) will not feature either.