Richardson didn't practice once again on Friday. With the rookie out, the Colts will start backup quarterback Gardner Minshew.
Richardson suffered the head injury during the second quarter of the Colts' 31-20 win over the Houston Texans in Week 2. He played two more drives before he was replaced by Minshew, who completed 19-of-23 passes for 171 yards and a touchdown.
Richardson had completed 6-of-10 passes for 56 yards and had three carries for 35 yards and two touchdowns before he was replaced.
Richardson was picked No. 4 overall by the Colts in this year's NFL Draft. He played college football at Florida.
Minshew has played for the Jacksonville Jaguars (2019-20) and Philadelphia Eagles (2021-22) during his career. Through two games this season, he has completed 19-of-25 passes.
Minshew was a backup for the Eagles this past season and completed 44-of-76 passes (57.9 percent) for 663 yards and three touchdowns against three interceptions.
Minshew signed a one-year contract with the Colts in March.
Indianapolis will look to win the AFC South for the first time since 2014. Indianapolis has not reached the playoffs since 2020.
The Colts are in their first season under coach Shane Steichen. He was the offensive coordinator for the Eagles the past two seasons and is familiar with Minshew.