Alonso said that despite feeling pain in his back for a couple of days, he doesn't think it is anything too serious. He said he thinks he should be back soon.
Alonso said he first felt tightness after he slid in Monday's game against the Rangers.
"This morning I woke up pretty sore. Just tried to continue to battle through it. Got it as loose as I could prior to today's game," Alonso said. "After I hit that double, just got really tight in the dugout and pretty sore. Just something that you just have to let it heal for a day or two and should be back in there."
Alonso appeared to struggle to pick up a ground ball in the top of the third inning.
"Anybody has any back issues, it kind of hurts to do anything," Alonso said. "I should be OK in a day or two. If anything, it's more good news than bad news."
Brett Wallace came in to pinch-hit for Alonso in the bottom of the third and also took over duties at first base.
Alonso is batting .282 with 35 RBIs and has hit safely in nine of his last 10 games at Petco Park. He doubled in his only at-bat Tuesday.
Beth Maiman is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.