Blaine Gabbert will relieve Colin Kaepernick on Sunday

When starter Colin Kaepernick departs Sunday’s preseason game vs. San Diego, Blaine Gabbert will have another chance to prove he’s got what it takes to hold the 49ers’ backup QB job this season. Coach Jim Harbaugh indicated Friday that Gabbert, the Jaguars’ former starting quarterback, would be first up in relief of Kaepernick in Sunday’s…