Lamar Jackson rushed for 26 yards in Baltimore’s 20-19 preseason win at Indianapolis on Monday night. (Darron Cummings/AP)

Lamar Jackson knows it, and so do the Baltimore Ravens.

If the Heisman Trophy winner is the guy who will eventually replace Joe Flacco, he hasn’t shown it yet. The latest bit of evidence came in the Ravens’ third preseason game, a 20-19 victory over the Indianapolis Colts on Monday night. Jackson, a first-round draft pick, completed 7 of 15 passes for 49 yards and a touchdown. But he has yet to top 50 percent in completions, no matter how sweet the TD pass may have looked.

“I don’t feel like I’ve performed at a high level yet,” Jackson said.

He’s right. And this is the preseason, when coaches look to see whether a guy with Jackson’s college résumé can carve up guys who won’t be on rosters next month.

“I came out cold,” Jackson said of coming in for Flacco. “I got to learn that when the vet is up. I have to stay warm through the process. I didn’t do a good job tonight. I started off slow . . . incompleting a lot of balls that I didn’t like, but I ended up throwing a touchdown.”

So far, Jackson has shown flashes while on the run, not while playing in the pocket, and he pointed out that he started slowly in college, too.

“That’s the great thing about Lamar. He’s confident. He’s going to keep competing,” Baltimore Coach John Harbaugh said. “He’s always going to believe that he can make the play to turn the game. He did a great job of doing that.”

His performances, along with the eternal question of whether Flacco is elite and the strong play of Robert Griffin III this preseason, present the Ravens with a dilemma. Do they go with Jackson as the backup? Do they keep three quarterbacks? Flacco has played well and shown no signs of relinquishing his job. But what if he gets hurt or struggles?

That would be a tough spot for a coach who might be feeling the heat, too. Since winning Super Bowl XLVII after the 2012 season, the team has gone to the playoffs only once (narrowly missing out with last year’s 9-7 squad). The Ravens have finished no better than second in the AFC North and overall are 40-40. Which increases the pressure on the 32nd overall pick in April’s NFL draft.

“There’s no question in my mind that he has a great future,” Harbaugh said.

It’s one to which Harbaugh’s inevitably will be tied as well.

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