invest early first-round picks on quarterbacks or to trade a boatload of assets to get into position to take them is a luxury that only a handful of NFL teams have enjoyed in recent years.

But just how long will it last for the Ravens? Flacco is 32 years old and now playing on one surgically repaired knee.

He’ll enter the 2017 season facing plenty of scrutiny as his play has dipped since 2014.

During the Ravens’ 8-8 season last year, Flacco ranked in the bottom part in the league among qualifying quarterbacks in categories such as yards per attempt, quarterback rating and interceptions.

“We have a championship-caliber quarterback,” Harbaugh said Wednesday at the start of the combine. “We have a guy we can go win with. We have a guy that’s capable of carrying a football team and has done it in the past, and we need to do everything we can to put a football team around our championship-caliber quarterback.

And then go to work onthe X’sandO’s, which our coaches are doing right now. Let’s build the X’s and the O’s and the schemes and the game plans to give our guys the chanceto be the mostsuccessful. Butthe No.

1 piece we have in place is the most important piece, and that’s the quarterback.”

Harbaugh’s vehement support of Flacco comes at a time when at least six teams don’t know who their starting quarterback will be in 2017. The San Francisco 49ers and new general manager John Lynch don’t have a single quarterback on their roster.

The Ravens are exploring the free-agent and draft quarterback classes, but they’re not pondering using the16th overall pick on Clemson’s Deshaun Watson, North Carolina’s Mitchell Trubisky or Notre Dame’s DeShone Kizer.

With Ryan Mallett heading to free agency, the Ravens instead are reviewing the backup quarterback market, which includes journeymen such as Brian Hoyer, Josh McCown and Case Keenum. They also are considering drafting a developmental quarterback, but with only seven picks and manyneeds, it’s notalockthatthey’lldothat.

Some quarterbacks who fit the criteria are Miami’s Brad Kaaya, California’s Davis Webb, Tennessee’s Josh Dobbs and Pittsburgh’s Nathan Peterman.

“We need a backup quarterback, certainly,”

Harbaugh said. “Ryan is not under contract right now, so we’re talking to Ryan.

We want Ryan back, and there are other veteran guys out there. The draft will definitely be part of that. We need a quality backup quarterback.”

After being drafted in 2011, Taylor was immediately installed as Flacco’s backup, a role he held for four seasons before signing with the Buffalo Bills and becoming their starter. Wenning, who played his college ball at Ball State, was drafted in 2014 as a developmental guy and the potential heir to Taylor. However, he didn’t stick and has failed to establish himself elsewhere.

Other than that, the Ravens have eschewed opportunities to select a quarterback, instead signing veteran backups such as Matt Schaub, Jimmy Clausen and Mallett the past two years.

Some teams invest more in developmental quarterbacks than others. Despite having the ageless Tom Brady, the New England Patriots used a third-round pick on Mallett in 2011, a second-rounder in 2014 on Jimmy Garoppolo and a thirdround selection on Jacoby Brissett last year.

The Seattle Seahawks have gone four straight drafts without selecting a quarterback, but they earned the ability because of their decision to use a third-round pick in 2012 on Russell Wilson despite having just signed free agent Matt Flynn to be their starter. As a rookie, Wilson beat out Flynn and has held the job ever since.

But finding and developing a guy in the middle rounds such as Wilson or Kirk Cousins, whom the Washington Redskins selected in the fourth round in 2012 after having already taken Robert Griffin III in the same draft, is easier said than done.

Arizona Cardinals coach Bruce Arians, whose starter Carson Palmer pondered retirement this offseason, called the decision on when to draft a developmental quarterback a “double-edged sword.”

“We want to win now because we feel like we have that window, but we have to take care of the future,” Arians said. “But if that guy is available for us … The ones that we’ve liked haven’t been available when we would have liked to have had them.”

Flacco doesn’t figure to go anywhere anytime soon. He’s still under contract for five more seasons and moving on from him at least over the next two years, if not three, would be crippling to the team’s salary cap.

But at some point, the Ravens will need to start enacting a plan for developing his successor.

“I think it’s a similar question that a lot of teams throughout the league are answering right now with aging quarterbacks,” NFL Network lead draft analyst Mike Mayock said lastweek. “Drew Brees is 38,TomBrady is 39, [Palmer is] 37, Ben Roethlisberger is getting older. I think there are a bunch of teams around the league saying: Who is next? And when do you pull the trigger and how high do you pull the trigger?” jeff.zrebiec@baltsun.com twitter.com/jeffzrebiecsun