Giles continued to play after the collision but left in the bottom of the fifth inning.
"I was feeling alright, it just kept swelling and my shoe kept getting tighter and tighter around my foot. It's kind of unfortunate," Giles said after Wednesday's game.
Black is hoping for a speedy recovery, especially since Giles has played a key role in the Padres' offense.
"I hope so, but we don't know," Black said of Giles' timetable. "He's got a sprained ankle, hopefully he's able to get back as quickly as possible. He's sore, he's walking around [but] not at 100 percent."
This is Giles' second injury of the season. He missed almost six weeks in May and June with a bone bruise in his right knee.
He has only been back since June 29 and is already batting .296 with 23 RBIs and two home runs for the season.
Giles did not enjoy sitting out during his first injury of the season and is hoping to be back by Friday's game against the San Francisco Giants.
"Pretty sore right now," Giles said. "I'll get some treatment tomorrow and be ready to go on Friday. It's a shame that it happened."
Giles was replaced by Rob Mackowiak on Thursday.
A Giant invasion: Maybe Black is not paying too much notice to the Giants' arrival tomorrow, but everyone else is.
The press box will be beyond capacity for the first two games of the series, which starts on Friday. They are sold out thanks in large part to Barry Bonds, who is still chasing the home run record.
Bonds needs one home run to tie Hank Aaron's all-time mark of 755 home runs.
"As we've maintained throughout this season, we are going to pitch according to the game, according to the situation," Black said. "There are so many variables that go into pitches to that caliber of a hitter. We'll take all those into consideration.
"I'm sure there's some thoughts in the back of all of our pitchers' minds. I think some probably relish the opportunity to face Barry."
San Diego starting pitcher Greg Maddux, Friday's starter, will be the first Padre to face Bonds. Maddux has allowed eight home runs to Bonds in his career.
Playing catch: That's precisely what pitcher Chris Young did prior to the Padres' game on Wednesday and came out of it just fine in his first real action since straining his left oblique in a start against Colorado on July 24.
"It's encouraging," Black said.
Young, who went on the disabled list retroactive to July 25, might throw off the mound before Saturday's game against the Giants.
"Tentative, but that could change depending on how he feels," Black said.
If all goes according to plan, Young (9-3, 1.82) could be activated from the disabled list prior to his scheduled start on Aug. 9 in St. Louis.
Lineup roulette: Another day, another different lineup for Black, who has been anything but predictable when it comes to filling out his lineup card.
On Thursday, Black inserted newcomers Mackowiak and Morgan Ensberg into the starting lineup, with Mackowiak hitting leadoff and playing right field and with Ensberg at third base.
"Rob is going to lead off the game. I am excited to see him play. Morgan is starting at third," Black said. "These guys are going to be part of it. We have these guys and we think they're going to contribute. They're good players and you've got to use them all, their whole team."
Friar notes: Pitcher Will Inman, considered the prized prospect the Padres got in the trade to Milwaukee last week for Scott Linebrink, made his debut with Double-A San Antonio on Wednesday. The 20-year-old right-hander allowed one run over six innings with five walks and four strikeouts in the Missions' 5-1 victory over Corpus Christi. ... Jake Peavy, who got the start on Thursday for the Padres, entered the game six strikeouts away from 1,000 for his career. He currently ranks behind only Andy Benes (1,036) in strikeouts in Padres franchise history. ... Milton Bradley has hit safely in 10 of his last 11 games. He's hitting .428 over his last 11 games with four home runs and 11 RBIs. ... Two of the three weekend games against the Giants (Friday and Saturday) are sold out, with about 5,000 tickets still remaining for Sunday's game. ... New hitting coach Wally Joyner was in uniform for Thursday's game.
On deck: The Padres open a three-game series against the Giants at 7:05 p.m. PT on Friday. Maddux (7-8, 4.20) gets the start for San Diego. San Francisco will counter with Matt Cain (3-12, 4.02).