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7/10/2014 5:10 P.M. ET

Umpire Johnson departs with possible concussion

SAN FRANCISCO -- Home-plate umpire Adrian Johnson exited Thursday's game between the A's and Giants at AT&T Park after just three innings because of a possible concussion resulting from a foul tip to his mask.

Crew chief Angel Hernandez, who began the contest at second base, took over duties behind the plate, leaving just a pair of umpires in the field.

Johnson took a hard foul tip off the front of his mask during Pablo Sandoval's first-inning at-bat. According to umpire supervisor Ed Montague, Johnson was being examined for concussion symptoms.

Jane Lee is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.