Alonso missed 34 games earlier this season with a fractured metacarpal bone in his hand. He returned from the disabled list on July 12, but the strength in his hand wasn't the same as it was earlier this year when he hit .284 with six home runs in his first 190 at-bats.
After returning from the disabled list in July, Alonso hit .278 with no home runs and four doubles and said he wasn't able to do the same things with his swing that he could before the initial injury.
"Yonder is doing great, he's going to be able to play defense," said Padres manager Bud Black. "We're comfortable with him throwing and are comfortable with him if he has to dive. There's motivation for Yonder to get back on the field."
He's running out of time. After Thursday's series finale against the Phillies, the Padres have only 17 games left in the regular season.
"I'm optimistic about it [returning]. But it's just a matter of time for this thing to heal," said Alonso, who noted that he'll likely have a grip-strength test when the team returns to Petco Park on Monday.
The Padres have used Kyle Blanks at first base, though rookie Tommy Medica -- who hit a home run on Wednesday for his first Major League hit -- got the start there again on Thursday.
Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.