The visitors make the trip to the West Midlands having also enjoyed a solid opening to the season, recording three points from their first two matches.
Birmingham City supporters spent the closing weeks of last season witnessing their side move closer to the relegation zone on a weekly basis, eventually only avoiding the drop to League One by two points.
Although fans will err on the side of caution, four points and two clean sheets from games against Brentford and Swansea City is a superb return, particularly with so many new faces linking up with the squad.
Birmingham will eventually have to show a greater cutting edge in the final third, something which may happen in future games after the arrival of Scott Hogan.
Nevertheless, Karanka has done a terrific job in turning pessimism into optimism in the matter of months, and another win here would keep the club among the early pacesetters.
Rotherham are another team who have been tipped to spend more time in the bottom half of the table than in the upper echelons, but the Millers have the potential to go under the radar this season.
Their opening-day win did come over second-tier minnows Wycombe Wanderers, opposition who conceded five goals at Blackburn Rovers in their next outing.
However, that success has eased the pressure on the Yorkshire side ahead of the game on Saturday, one which Paul Warne will feel is winnable with the right approach.
Like Blues, Rotherham are finding goals hard to come by, but Warne will have confidence in a defence which have only conceded twice in their opening three games in all competitions.
Birmingham City Championship form: WD
Birmingham City form (all competitions): LWD
Rotherham United Championship form: WL
Rotherham United form (all competitions): DWL
Wes Harding is in line to face his former club, just over a month since completing a transfer from St Andrew's.
Barring any late fitness issues, Karanka is unlikely to make any alterations to his Birmingham XI.
New arrival Mikel San Jose will be named among the substitutes at best, joining recent arrival Hogan in having to remain patient for an opportunity.
Birmingham City possible starting lineup:
Etheridge; Colin, Dean, Friend, Pedersen; Sunjic, Clayton; Sanchez, Toral, Bela; Jutwiewicz
Rotherham United possible starting lineup:
Blackman; Harding, Ihiekwe, A.MacDonald, Mattock; Ogbene, S.MacDonald, Lindsay, Sadlier; Hirst, Smith
We say: Birmingham City 2-1 Rotherham United
While Karanka is placing priority on ensuring that his side are solid defensively, there will be certain games this season where they have to show a greater attacking intent. This fixture is one of those occasions, and we feel that Blues will be able to prevail by the odd goal in three.