Castro ranked second among all National League shortstops in batting average and hits, trailing the Rockies' Troy Tulowitzki.
Prior to the All-Star break in 2013, Rizzo was batting .241 with 13 home runs and 54 RBIs. This year, he was batting .286 with 17 home runs and 44 RBIs going into Saturday's late game.
Rizzo leads NL first basemen in home runs. Could he or Castro make it to the All-Star Game? They'll find out July 6 when the NL team is announced.
Fans can cast their votes for starters at MLB.com -- online or on a mobile device -- using the 2014 All-Star Game MLB.com Ballot Sponsored by Experian until Thursday, July 3, at 10:59 p.m. CT. The 2014 All-Star Game will be played at Target Field on Tuesday, July 15 on FOX.
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.