Here’s what we know from the 31-word statement released by the Ravens shortly before 7 p.m. Friday, just over 24 hours before the biggest game of their season: John Harbaugh will return for his 12th season as coach next year. His contract expires after next season. Both sides are working on an extension.

Here’s what we don’t know: the terms of his return, and just how much say he’ll have in determining them.

Harbaugh is already well-paid. He is respected by his players. He has managed the ascendance of quarterback Lamar Jackson and the reinvention of their offense with grace. But when the Ravens faced the Los Angeles Chargers on Saturday night, their postseason hopes hinged on a quarterback-heavy ground game. What makes their offense unusual and effective is also what might make it unsustainable in 2019 and beyond.

There are many paths to success in the NFL, but the arc of the league ultimately bends toward the forward pass. The Ravens have had the NFL’s top-ranked defense throughout the season largely because of perhaps its deepest group of cornerbacks. The Ravens now have the NFL’s best rushing attack largely because they ask one of the league’s best athletes to attack defenses with his legs.

It is a risk under center, one Harbaugh has acknowledged. Football’s rules are built to protect pocket passers, not quarterbacks who are routinely asked why they don’t slide more in the open field. There is a reason Joe Flacco lasted 10-plus years as a starter, and Robert Griffin III less than three. The most important position in football is quarterback, and the safest place for a quarterback is the pocket.

Some of Jackson’s runs are his call, the product of a supremely confident rookie reading a defender on a zone-read play and jetting into the open field. But coordinator Marty Mornhinweg, long a target of criticism for his Flacco-led offenses, is also a caretaker. So is Greg Roman, in his first year as assistant head coach after helping to rejuvenate the Ravens’ running game last season with Alex Collins. Harbaugh has praised their work in adapting to Jackson’s skill set, but defenses catch up, too.

“The players deserve credit, and the coaches deserve credit,” Harbaugh said Monday of the team’s rushing success. In their win Sunday over the Tampa Bay Buccaneers, the Ravens became the first team since the 1976 Pittsburgh Steelers to post at least 190 rushing yards in five straight games. “I think the game-planning has been excellent, and Greg Roman spearheads that, along with Marty and [running backs coach] Thomas Hammock and [offensive line coach Joe D’Alessandris], all of our coaches.”

In declaring Harbaugh’s job safe, playoffs or no playoffs, Ravens officials have offered a tacit endorsement of the team’s philosophical direction, even as little about the team’s efficiency has changed. For better or for worse.

Before Jackson made his first start, the Ravens defense was holding opponents to an NFL-best 4.7 yards per play; five weeks later, it’s 4.8 yards per play and still No. 1. Under Flacco, the offense averaged 5.2 yards per play, fifth worst in the NFL; under Jackson, it’s still 5.2 yards per play. The change from a pass-heavy attack to a run-reliant offense accounts for some of the stasis, sure. But the Ravens have also feasted on some of the worst rushing defenses in football.

Given the crowded AFC wild-card picture, Saturday’s game already amounted to a tryout for the playoffs. Now it might be an important audition for the Ravens’ offensive staff. Mornhinweg this week declined to call the Chargers defense the best Jackson will have seen as a starter, but it is. The Chargers do not stop the run as well as, say, the Ravens do, but they also do not rank among the NFL’s seven least efficient rushing defenses, as the Ravens’ past five opponents do, according to Football Outsiders.

Mornhinweg and Co. have proven capable of offensive reinvention, both in the offseason and midway through the season. After being among the NFL’s more reluctant adopters of RPO plays, they had better integrated them into their offense by the time training camp started this July. And after calling on Flacco to throw as many as 56 times in a game this season, they’ve successfully audibled to an offense in which Jackson hasn’t attempted even 30 passes in any of his five starts.

Jackson, too, should improve after an offseason in which he can worry less about NFL defensive concepts and more about his footwork. Over his freshman and sophomore years at Louisville, he went from being an average passer to No. 27 nationally in quarterback rating.

But the ambiguity surrounding Harbaugh’s possible extension, and the impending promotion of assistant general manager Eric DeCosta, invites speculation about the future. Ravens officials have given Harbaugh at least another year to lead the team to success. Harbaugh has been most successful this season when he has relied on an offense that holds its breath every time Jackson is tackled. What happens when every franchise’s greatest need — a healthy and successful quarterback — collides with a playing style that undermines it?

The Ravens’ decision to keep Harbaugh has answered the team’s most important offseason question. The coaching staff he returns with will be just as revealing.

jshaffer@baltsun.com

twitter.com/jonas_shaffer