INDIANAPOLIS – Anthony Richardson’s second season is over. The Indianapolis Colts’ injury-plagued starting quarterback did not practice Friday because of back spasms and a disc issue in his lower back and has been ruled out of Sunday’s season finale against Jacksonville. "Just didn’t make enough progress this week," coach Shane Steichen said. Joe Flacco will start Sunday against the Jaguars. Richardson has missed two full weeks of practice along with last Sunday’s loss to the New York Giants that eliminated the Colts from playoff contention. Initially, Steichen said Richardson wasn’t practicing because he was "very sore" following the 38-30 win over Tennessee, but then a team source elaborated that Richardson was dealing with severe back spasms that were limiting his mobility. Richardson revealed Wednesday he’s dealt with back spasms since "about eighth grade," but added an MRI last Friday detected a "disc thing." He said he was feeling much better than the previous week when Richardson said he "could barely move" and at times had to crawl around his house. Friday ended any speculation about whether he might be able to play in the final game of his second season. Richardson now has missed 17 of 34 career games due to injury. He also was benched for two games this season. The Colts are 8-7 with Richardson as a starter, including 6-5 this year, but his development as a passer seemingly has regressed. He completed 59.5% of his passes in four starts as a rookie, but that’s fallen to 47.7% in 11 starts in year 2. That’s the worst percentage in the NFL by a wide margin – the next worst is Carolina’s Bryce Young at 59.7% - this year. Richardson’s 47.7% (126-of-264) will be the lowest in club history among QBs with at least 200 attempts. He "surpassed" Jack Trudeau’s 48.9% in 1986. The only other quarterback to finish with less than 50% completions: Mike Pagel, 49.7% in 1983. Richardson said the disc issue isn’t "that severe" and surgery won’t be required. Steichen agreed. "I don’t think it’s that severe," he said, adding the team doesn’t believe the back/disc issues will persist. "I don’t think so. I mean... we’ll obviously have to monitor it with the doctors and him going forward." Over 300 players converge on Indy every year for the NFL Scouting Combine and the overriding priority is determining the health and exploring everyone’s injury history. There is no evidence Richardson missed time at Florida or with the Colts because of back issues prior to what’s going on now. "Our trainers and our doctors do extensive research on that stuff and there was no issues that were shown," Steichen said. "That’s not to say he didn’t have anything when he was really young, and it was just something that flared up on him last week." Richardson didn’t exactly allay concerns about the back/disc issues moving forward. "It might be chronic," he said, "but there’s plenty of ways to prevent it going on in the future. Now that I know what it is, I can find certain ways to stay out of certain positions (and) just make sure I’m healthy, 100%." Brents returning? The final game of the season might be an opportunity for JuJu Brents to get back on the field. The second-year cornerback and product of Warren Central H.S. has practiced the last three weeks while finishing his rehab from a knee injury suffered in the season opener against Houston. Brents was placed on the injured reserve list Sept. 10. "He had a good week," Steichen said. The Colts will have to add him to the active roster, which will require making a corresponding move to make room for Brents. "It’s been a solid week of practice," Brents said. Returning for the final game "would be big," he added. "I always had that goal in mind: ‘I’m going to play again this year.’ I just kept repeating that to myself. "So, if I get the opportunity, it’s a good thing." Brents' lack of availability has mirrored Richardson’s. He’s missed 23 of 33 games because of a variety of injuries since the Colts selected him in the second round of the 2023 draft, No. 44 overall. Brents' rookie season was limited to nine games and eight starts because of wrist, hamstring, quad and ankle injuries. He also underwent a clean-up surgery on an ankle in June, missed time during training camp with a shoulder injury and required a procedure to address a broken nose. You can follow Mike Chappell on Twitter at @mchappell51.