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As the Ravens prepare for the most important game of the season, coach John Harbaugh said their starting quarterback is day-to-day.

“Well, it’s to be determined,” Harbaugh said. “I mean, he’s coming off a very serious injury. And he’s working at it. I saw him here today working at it. I think we’ll know a lot more Wednesday.”

He later added that Lamar Jackson would play if healthy.

“If Lamar’s ready to go, he’s playing,” Harbaugh said. “That’s it. For sure.”

Jackson has dealt with numerous lower-body injuries through the season, including a hamstring injury that kept him out for three games, before suffering a back contusion in the Week 16 game against the New England Patriots.

Jackson took a knee to the back just before halftime and was not able to return to the game. He missed all of practice and the Week 17 game against the Green Bay Packers.

Harbaugh said Jackson showed improvement throughout the week but that it was “not good at all” earlier in the week.

“That was cause for optimism,” Harbaugh said.

With Jackson out, backup Tyler Huntley quarterbacked the Ravens to a dominant win, keeping the Ravens’ playoff chances alive. He also helped the Ravens beat the Chicago Bears.

“To see it [Huntley’s improvement] come to fruition in these games and to win these big games is really awesome,” Harbaugh said.

The Ravens just needed the Cleveland Browns to beat the Pittsburgh Steelers to give them a chance to get into playoffs. Huntley called Browns quarterback Shedeur Sanders on Sunday morning. Sanders and the Cleveland Browns defense did just enough to beat the Steelers in a 10-6 win.

Now, the Week 18 game between the rivals is win or go home. With a Pittsburgh win, the Steelers would be in because they would have the better head-to-head record. With a Baltimore win, the Ravens would be in because they’d have the better record against common opponents.

Jackson, who enthusiastically cheered his friend and backup on through the end of Week 16 and the win in Week 17, expressed frustration in the locker room after the Patriots game over how much his health has limited him this season.

He’s had the third-worst completion percentage and fourth-worst quarterback rating of his eight-year career. He’s also been sacked 33 times, the third-worst mark of his career.

This season, the Ravens are 6-6 with Jackson behind center.

The decision will be made by the doctors and medical staff.

“The coaches aren’t deciding who plays from a medical standpoint,” Harbaugh said.

Despite the Ravens’ success with Huntley, if Jackson is healthy, there’s no debate who will start.

“The fact that we have a lot of confidence in Tyler is a real big positive, a real plus, but it doesn’t factor into whether Lamar plays,” Harbaugh said.