"That pile just kept getting bigger and I wanted him out of it," Tomsula said Wednesday. "This is a guy I care about a lot."
The first-year coach emphasized that the move could be temporary and that he wanted Kaepernick to take a step back, watch, learn and keep working to improve. Kaepernick had started 47 consecutive regular-season games before this change.
The approach of sitting a quarterback so he can regain his bearings has been tried by other coaches, such as with Robert Griffin III in Washington and Mark Sanchez, both peers of Kaepernick, when he was with the Jets. It even happened with Gabbert when he struggled as a starter in Jacksonville and was replaced by Chad Henne.
None has re-established himself as a full-time starter, although Gabbert has an opportunity to do so with an offense that has been inept across the board for most of the season.
"Everyone on offense needs to play better, coach better," Tomsula said.
Though there was consultation with management and ownership about the change at quarterback, Tomsula said he made the final decision to bench Kaepernick.
Tomsula twice said that this change was not comparable to Kaepernick's replacement of Alex Smith in 2012 -- a decision made by Tomsula's predecessor, Jim Harbaugh. That move came when Smith had played well but got hurt and Harbaugh stuck with Kaepernick. The move paid off as the 49ers made it to the Super Bowl, losing 34-31.
Kaepernick's rapid success, promise and confounding of defenses led to stardom on and off the field. The same was true of the 49ers, who were one of the best teams in the NFL under Harbaugh, feared on offense and defense.
The rapid turn of fortunes for franchise and the highly athletic quarterback has been stunning.
Much of Kaepernick's and the 49ers' demise has been laid at management's decision to let Harbaugh leave after last season. Key players like Frank Gore, Michael Crabtree, Anthony Davis, Justin Smith and Patrick Willis on both sides of the ball departed or retired. Early this week, San Francisco also traded tight end Vernon Davis, one of the best at his position just a few years ago, but a non-factor the past two seasons.
The offensive line has been banged up and inconsistent and the 49ers' only game-changing playmaker at the skill positions has been Kaepernick. The quarterback has tried to work on his mechanics, passing touch and other fundamentals but through the season, he fell back into bad habits, made poor decisions and failed to move an offense.
San Francisco is last in total offense and last in scoring offense.