Arians had been dealing with the flu earlier in the week (he missed practice Thursday), and initial indications are that Sunday's setback may be related. The Colts announced, per multiple reports, that Arians was fine but required further evaluation.
In his stead, quarterbacks coach Clyde Christensen called the offensive plays for the Colts. Christensen has been with the Colts since 2002 and was the offensive coordinator during the 2008 season.
This week's game was just the second for the Colts with head coach Chuck Pagano back on the sideline. Pagano missed more than two months of the season while undergoing treatment for leukemia. Arians filled Pagano's role on an interim basis and helped lead the Colts to an 11-5 record and a surprising playoff berth.
This latest development presented another obstacle for rookie quarterback Andrew Luck, as he prepped for his first playoff game. Already, Luck faced the prospect of a Ravens defense fired up for Ray Lewis' (and possibly Ed Reed's) final home game -- Lewis announced earlier in the week that he would retire when the season ended.
Luck finished 28 of 54 for 288 yards and an interception, and he was hurt by a Colts offensive line that allowed three sacks and a lot of other pressure, as well as a group of receivers that consistently dropped balls. The Ravens, meanwhile, played just their fourth game with Jim Caldwell calling the shots as offensive coordinator. Caldwell took over that position from Cam Cameron prior to Week 15 -- this will be Caldwell's first postseason game as an offensive coordinator, as well.