"I guess it's a possibility," Giants manager Bruce Bochy said of the disabled list. "Anytime a guy gets a MRI and waiting on the results, that's always a possibility. I just can't comment on it until we get the results."
Span, who signed a three-year, $31 million deal with the Giants before the start of the season, entered the series against the D-backs batting .253 with 30 RBIs in 76 games this year.
The club could use some good news. Outfielder Gregor Blanco, who replaced Span on Friday and Saturday, was scratched from the starting lineup Sunday because of a sore left knee. Veteran left fielder Angel Pagan was also not in the starting lineup Sunday with what Bochy described as "general soreness."
Jarrett Parker started in center field and Brandon Belt, originally slated to be off with Buster Posey starting at first base, started in left field Sunday.
• Injured starter Matt Cain (right hamstring) threw 46 pitches in 3 1/3 innings during his first rehab start for the Arizona League Giants on Saturday night. He allowed two runs on three hits, including one home run, and struck out six.
Cain¸ who is expected to make another rehab start Thursday or Friday, showed good command with a fastball in the 90-91 mph range, Bochy said.
The right-hander could need up to two more starts to reach a 90-pitch threshold, the manager added. Cain was placed on the disabled list with the injury for the second time this season June 14.
• Infielder Kelby Tomlinson went 2-for-4 with one RBI as the designated hitter for Class A Advanced San Jose on Saturday night. He will DH again Sunday and depart for Triple-A Sacramento on Monday.
Jesse Sanchez is a national reporter for MLB.com based in Phoenix. Follow him on Twitter @JesseSanchezMLB and Facebook. This story was not subject to the approval of Major League Baseball or its clubs.