OWINGS MILLS, Md. (AP) — Keeping three quarterbacks was not an easy decision for Baltimore Ravens coach John Harbaugh, who hasn't had that many QBs on his opening day roster since 2009.

Now he's got to determine the best way to use them.

Joe Flacco will start Sunday against the Buffalo Bills, but Harbaugh isn't revealing whether the backup will be Robert Griffin III or rookie Lamar Jackson.

Griffin has 42 games of NFL experience and Jackson is a slick-footed runner who could be a threat near the goal line, as evidenced by his three rushing touchdowns during the preseason.

Whether Griffin or Jackson receives spot duty remains to be seen. At this point, Harbaugh isn't even sure how many quarterbacks will be on the active list each week.

"It won't be any more than three, it won't be less than two," he said with a grin on Monday. "So, we'll see. I really don't know."

This much is certain: There's a lot to like about having a former Super Bowl MVP (Flacco) and a pair of Heisman Trophy winners at the most important position on the field.

"I'm excited to have three quality quarterbacks," Harbaugh said. "It makes our quarterback room stronger. That's really what it does."

Griffin went 27 for 41 for 243 yards and two touchdowns this summer. He also proved to very helpful in guiding Jackson through his first NFL camp.

Still, Harbaugh said after the preseason finale against the Washington Redskins last week that Griffin's place on the 53-man roster "depends on the rest of the math."

After sitting out the Redskins game, Griffin expressed absolutely no anxiety in awaiting the Ravens' decision.

"When you put in the hard work and you've done everything you possibly can to put your best foot forward and try to show the team that you deserve to be here, there's no stress," he said.

After the Ravens did the math, Griffin was too good to subtract from the equation.

"From a team standpoint, you can look at it any kind of number of different ways," Harbaugh said. "There are a lot of factors that were considered, and that was the way it shook out."

After going three years without a playoff berth, the Ravens probably can't afford to have a rookie take over if Flacco gets hurt or plays poorly over an extended period of time. Griffin went to the postseason with the Washington Redskins in 2012 and showed during the preseason he can run this offense.

Though Jackson showed improvement in each of his five appearances, at this point he's still going through the learning phase. Fortunately, he has two willing teachers in Flacco and Griffin.

"You can never have enough experience, good guys, good people to draw on," Harbaugh said. "He just learns so much from Joe and from Rob."

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