Triple-A left-hander Tyler Skaggs appears to be the front-runner to make the start.
• Outfielder Gerardo Parra was out of the lineup for the second straight night after diving headfirst onto the warning track during Monday night's game and suffering cuts to his face and bruises to his body.
• Gibson talked a little while back with Giants manager Bruce Bochy, who will skipper the National League All-Star team.
One of the players whom Gibson made a case for Bochy selecting to the team was first baseman Paul Goldschmidt.
"He would enjoy his time [with Goldschmidt]," Gibson said. "And when he's done coaching, he's a guy that he would want to have coached, had a chance to spend some time with and I just wanted to relay that."