Hayes will not play because of a chronic knee problem that has progressively worsened throughout the season. Jaguars coach Gus Bradley said Hayes will undergo arthroscopic surgery to repair cartilage damage and remove loose bodies in his right knee.
"It's hard but it's a smart decision, take care of the body and just get ready to start off in the offseason full-go without being held back out of anything," said Hayes, who missed last week's game against Tennessee. "It built up as the season went on. ... When the body says you can't do it, you've got to go with the body."
Hayes was the Jaguars' third-leading tackler (78) and he also has two interceptions and three pass breakups.
Gratz (32 tackles, two interceptions) suffered a sprained left ankle in last Sunday's loss to Tennessee.
With Hayes and Gratz out, the Jaguars (4-11) will be without four defensive starters against the Colts. Linebacker Russell Allen (concussion) and defensive tackle Roy Miller (shoulder) were both placed in IR within the last two weeks.