The ball struck him on the helmet and its impact crumpled him to the dirt.
With a left-hander on the mound for Arizona, the Giants might give Buster Posey a start at first base in place of Brandon Belt and go with Nick Hundley behind the plate.
Posey told teammates that he felt normal, and that he was not experiencing the symptoms he expected.
Ryan Owens had visited the Giants in spring training several times.
"Yeah, he seems fine".
"He's doing OK", said Giants manager Bruce Bochy. If this were the case past year, Trevor Brown would be the guy stepping in.
The Giants added no insult by losing their home opener. That 6-1 mark - highlighted by a weekend sweep of the defending American League champion Cleveland Indians - was built on a potent attack that was producing 6.86 runs a game, tops in baseball. Mathis threw to Walker covering the plate, but his throw was wild too. So Panik scored, and Jarrett Parker dashed home as well. His role as cornerstone of the offense, in addition to catching the lauded pitching staff fronted by Madison Bumgarner, has earned him a very deserved reputation as a level-headed mentor, despite having just turned 30 years old. First baseman Paul Goldschmidt got the ball in almost the same place where Walker had been, and his throw back home was too late as Parker slid across safely.
"Just a lovely lady", Bochy said. Joe Panik played for over a week after getting hit in the head last season and then ended up missing 23 games.
Matt Moore pitches a great eight innings and leaves with a three-run lead. He was tagged for five runs on six hits and a walk with one strikeout across three innings in his first Triple-A start of the 2017 season. And Melancon shut the door.
"This is his second start of the year", Bochy said. "Could I have sent him back out?"
Hundley walked up to Bochy during the game Monday and joked, "it's about time you hit me cleanup".
The Giants also considered their own history with concussions.
But the Giants are also wizened enough to know that they can not know for sure. "That's a moment when you hold your breath". "I enjoyed it. I got fired up there".