A’s Josh Reddick out with back issue

Right fielder Josh Reddick was scratched from Oakland’s lineup two hours before game time at the Coliseum.

Reddick has back stiffness, the team announced. Coco Crisp wound up in center field, with Jake Smolinski shifting over to right.

Reddick was right in the midst of Oakland’s postgame celebration following Crisp’s walkoff single in the 13th inning Friday night, so it’s possible he tweaked something in the middle of the mass jumping around on the field.

Susan Slusser is a San Francisco Chronicle staff writer. Email: sslusser@sfchronicle.com. Twitter: @susanslusser