The Ravens announced that Robert Griffin III was inactive, which means Baltimore suited up two quarterbacks in Flacco and Jackson.
Going with Jackson could indicate that the Ravens intend to use him in two-quarterback plays with Flacco or in specialized packages for Jackson, especially in the red zone, where he was most effective in the preseason. Coach John Harbaugh said in June that Jackson would be active on game days, but Harbaugh wouldn't disclose the No. 2 quarterback leading up to the opener.
Jackson, the 2016 Heisman Trophy winner, finished the preseason strong, posting a 103.2 passer rating in his last two games. He ran for 136 yards (12th-most by any player in the preseason this year) and scored three touchdowns.
Asked four days ago if he is ready to take the field in any capacity, Jackson said: "Absolutely. I've been preparing for it through the OTAs, rookie minicamp. I'm just ready."
Griffin, the No. 2 pick in the 2012 draft, was more efficient and consistent than Jackson in training camp and preseason. He would likely start if Flacco misses any games.
With him on the roster for Week 1, Griffin's $1 million salary is guaranteed.
But the Ravens are intrigued by Jackson's playmaking ability, which can boost last year's No. 27 offense.
Jackson came in for Flacco in the third quarter, after Flacco went 25-for-34 for 236 yards. Jackson did little more than hand off the ball after entering with a 40-0 lead.
Griffin's impressive play came after he was out of the league last season. It led the Ravens to keep three quarterbacks for the first time since 2009.
Griffin prepared for the possibility of not playing.
"I will be understanding of that throughout the season and whatever may be," he said Friday.
The Associated Press contributed to this report.