"He can cover the ground, and he can also throw to stop you from scoring on the double from first base [and] limit triples," manager Dusty Baker said Monday afternoon. "He throws better than McCormick and [Jake] Meyers, who is not quite ready."
Siri, 26, played 21 games for the Astros this year including five starts in center. He will bat eighth in Monday's lineup.
It might be Siri's lone start as Meyers is close to returning after suffering a shoulder injury attempting to catch a ball over the outfield wall against the Chicago White Sox in the ALDS.
"He is doing a lot better," Baker stated. "He could probably get a start in these next two days, maybe as early as tomorrow [Tuesday]. Every day is important when you are fighting an injury."
Game 3 will be Siri's first at Fenway Park in his career.
"My first time playing in the postseason in the big leagues and to do it in center field at Fenway Park, it means a lot to me, and I'm really excited about it," Siri said through a translator. "It's a big center field, very deep. A lot of room to maneuver. I think I have an opportunity to make some good plays out there in center."
Siri hit .304 with four home runs in 46 at-bats for the Astros this season.