It's unknown how long Bouman will serve as the primary backup because there is no timetable for Smith's return from a tonsil infection.
Harbaugh said: "It could be weeks, and it could be next week."
Baltimore Sun reporter Edward Lee contributed to this article.
Season opener: Bengals @Ravens, Sunday, 1 p.m.
TV: Ch. 13
Radio: 97.9 FM, 1300 AM
Line: Bengals by 1 1/2
BEST AND WORST OF KYLE BOLLER
BEST
Nov. 14, 2004 (Ravens 20, Jets 17, OT): Boller connected on two TD passes to Clarence Moore to rally the Ravens from a 14-0 deficit before directing a seven-play, 32-yard drive to set up Matt Stover's game-winning field goal. Boller was 6-for-8 for 81 yards on his final three drives after going 13-for-25 for 132 yards on his first nine.
Dec. 19, 2005 (Ravens 48, Packers 3): Boller out-dueled Brett Favre on Monday Night Football, throwing for 253 yards and three touchdowns. He shredded the NFL's top-ranked pass defense, completing 19 of 27 passes (70 percent) and producing a career-best 136.8 quarterback rating (out of a possible 158.3).
Dec. 17, 2006 (Ravens 27, Browns 17): Coming off the bench to replace the injured Steve McNair, Boller helped the Ravens secure their first playoff berth in three seasons. With the score tied at 17, he hit Demetrius Williams for a 77-yard touchdown.
WORST
Oct. 10, 2004 (Ravens 17, Redskins 10): Boller was picked off on three straight possessions and over a span of eight throws. Each of his career-high three interceptions set up the Redskins in Ravens territory, but the Ravens' defense held them to 10 points. It marked his career-low quarterback rating (22.9).
Nov. 13, 2005 (Jaguars 30, Ravens 3): Boller threw three interceptions, the result of nonstop pressure applied by Jacksonville. He was sacked four times, including once when he was sandwiched between two Jaguars. After that sack, Boller was 10-for-21 the rest of the game.
Dec. 11, 2005 (Broncos 12, Ravens 10): Boller stymied the Ravens, with two of his three turnovers (two interceptions and a fumble) coming in the red zone. The most inexplicable mistake came one play after the Broncos fumbled at midfield in the fourth quarter: Boller fumbled while on the run with no one near him.
