The first quarterback to recover - Smith or Boller - could win the job. If neither is healthy, the Ravens would have no choice but to start rookie Joe Flacco, their first-round draft pick.
Could the Ravens' quarterback competition be settled by default?
"It's weird how things work," tight end Todd Heap said. "But we still have a couple weeks before we really need to go."
The problem is the Ravens don't have any idea who will start Thursday's preseason finale, the last time the quarterbacks can make a significant run at the job.
If Smith has recovered, he will be the Ravens' starting quarterback against the Atlanta Falcons, Harbaugh said.
But Smith, who came down with "a viral illness" Friday, remained sidelined yesterday and stayed home to take antibiotics.
Harbaugh said Smith's tonsil has "swollen up" and didn't know whether the 2006 Heisman Trophy winner had tonsillitis.
A local radio station reported that Smith had his tonsils removed yesterday, but the Ravens said they were unaware of any procedure. A source close to Smith said the second-year quarterback had simply received treatment at a hospital.
"We expect [Smith] to be ready to play, but that's not for certain," Harbaugh said.
The Ravens have wanted to get an extended look at Smith, who was supposed to play three quarters in Saturday's preseason game before getting sick. In two preseason games, Smith has had limited chances in the passing game, completing eight of 17 throws for 99 yards.
If he can play Thursday, he will go at least into the second quarter.
"We need to look at Troy," Harbaugh said. "I don't think that's changed from what we talked about last week. If Troy can go, he's going to play a lot in the game."
If Smith can't play, the Ravens would prefer to start Boller. But Boller is nursing an injury to his throwing shoulder and appears questionable to start at this point.
Boller was expected to test it by throwing passes under 20 yards. However, he did not attempt a throw during the 20-minute media viewing portion of practice.
Boller has not met with the media since being injured last week.
If Smith and Boller can't play, the Ravens would start Flacco for a second straight game.
Just 10 days ago, Harbaugh said Flacco was a long shot to win the job because he had been outplayed by Smith and Boller.
Now, Flacco could be playing himself back into the Ravens' quarterback race.
"I think he's in the mix because we have two quarterbacks who aren't able to practice," Harbaugh said. "The big picture hasn't changed dramatically in the sense that he's a rookie and we've got two guys who were ahead of him going into this situation that came up right before the game. That's kind of where we're at."
The Ravens did not want to rush Flacco into the starting job because of Boller's struggles as a rookie starter in 2003. But the Ravens were impressed by the way Flacco responded in his first start Saturday, when he went 18-for-37 for 152 yards and a touchdown.
The only NFL team that has decided to start a rookie this season is the Atlanta Falcons, who recently anointed Matt Ryan, the No. 1 quarterback chosen in the draft.
Asked where he stood in the Ravens' quarterback battle, Flacco said: "I really don't know what they're thinking, but all I know is that I got to prepare myself like a starter."
The Ravens can only hope that their cloudy quarterback picture will clear up after the final preseason game.
"It's a unique situation we have here," wide receiver Derrick Mason said. "All three of them are still in the bag right now, and I guess after this game we'll empty the bag and see who is the starting quarterback."
Next: Ravens vs. Falcons, Thursday, 7 p.m.
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