"I think ultimately Justin will be very involved in those decisions," said San Diego assistant general manager Josh Stein. "You're up against the end of the season. I think if Justin gets back physically to the point where he can go out and help us win, I think he's going to want to be out there.
"But we're still pretty far away from making a determination."
Upton was pursuing Logan Schafer's opposite-field ball down the left-field line in the first inning Wednesday when it appeared as if he lost his footing just as he reached the padded fence, with his head hitting the padding. He was able to retrieve the ball and throw it back to the infield as Schafer settled for a triple. Upton remained on his back for several minutes before leaving with his arm wrapped around a trainer for support.
"I think he's doing better. It's obviously scary any time a player hits their head and kind of goes down in that regard, but we got out there quickly and he responded to all the tests very well," Stein said.
The Padres could play their final series of the regular season without their top two middle-of-the-order bats in Upton and right fielder Matt Kemp.
Before Wednesday's game, the team announced that Kemp -- who knocked in his 100th run of the season on Tuesday -- would not play in the final five games of the regular season after suffering a partially torn tendon in his right middle finger.
Now it seems Upton could join Kemp on the bench for the final three games of the season.
If Upton is indeed done, he will have finished his first season in San Diego with a .251 average, a team-high 26 home runs and 81 RBIs.
On Thursday, Wil Myers got the start in left field for the Padres. Some surmise he might begin the 2016 season there if Upton departs.
Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.