HOUSTON -- The good news for the Padres is that Major League ERA leader Chris Young is feeling better after straining his oblique this past Tuesday.

The bad news is that it's not healing quite fast enough for him to make his next start.

San Diego announced that the right-hander will miss his scheduled start Sunday against the Astros, and a pitcher from Triple-A Portland will be promoted to start the finale of the four-game series at Minute Maid Park.

"We want to make sure we're doing the right thing for this injury," manager Bud Black said. "This is typically not a quick-healing injury. It is optimistic that he's feeling better, but I think this is a slow healing situation."

The next step for the Padres is to determine whether Young's injury will lead to a stint on the disabled list. That determination will be made Saturday afternoon based on the progress he's made to that point.

"It feels better today than yesterday," Young said. "It's encouraging. It easily could've been the same or worse."

For comparison, Houston closer Brad Lidge suffered the same oblique injury last month, and it took him approximately two-and-a-half weeks and a trip to the DL before he was able to throw at 100 percent. While the timetable obviously varies for each player, the precedent suggests Young may need more time to heal.

Tentatively, Young's next scheduled start is Saturday, Aug. 4 at home against the Giants.

Appeal dropped: Catcher Michael Barrett dropped his appeal of the one-game suspension given to him last Tuesday and sat out Friday's game against the Astros.

The suspension left the Padres with just one catcher and only 11 position players.

"We felt that with [Jake] Peavy pitching, with his ability to swing the bat and hopefully his ability to pitch deep into the game -- that might give us more of a chance to stay away from our bench," Black said.

Barrett was ejected in Sunday's 9-0 loss to the Phillies for arguing balls and strikes.

Leadoff success: While the Padres offense as a whole has scuffled over the past month, that certainly hasn't been the case for right fielder Brian Giles.

Since his return from the disabled list on June 29, the San Diego leadoff man is hitting .333 with a .462 on-base percentage along with seven doubles, a home run and 12 runs scored. He's reached base in 21 of those 23 games, and in that span he's raised his batting average from .276 to .295.

"That first game off the disabled list, I saw the ball a lot better than I anticipated," Giles said. "The key to my success is my knowledge of the strike zone. I've been able to get myself in some good hitting counts and also draw some walks, and I'm waiting until my timing catches up."

He's become an even bigger force in the midst of the Padres' current seven-game road trip. Entering Friday, he was 8-for-18 with two doubles on the road trip, and he's had multiple hits in each of the past three games.

"He's seeing the ball really well," Black said of Giles. "He looks very comfortable in the box. He's swinging at strikes and working counts. His swing is really solid. He has the best on-base percentage of all leadoff hitters in the game [since his return]."

Giles is now just 15 runs away from notching the career milestone of 1,000 runs scored.

"The production I look at with [Giles] is runs scored," Black said. "His job is to get on base and hopefully score a run. When there are opportunities out there, I think he can hit with runners in scoring position for a nice average too. But it's all about scoring runs."

But despite the production at the top of the order, the Padres offense still isn't clicking. They've scored more than five runs just once in the month of July, and they're 5-9 since the All-Star break. Making matters worse, they're now 1-6 in their last seven games.

"For our offense to be successful, we've got to have at least four guys going at the same time," Giles said. "We've only been able to get two or three of us going, and sometimes it's spread out throughout the lineup. That makes it tough for us as an offense."

Familiar face: The Padres faced former starter Woody Williams on Friday for the first time since he left San Diego in free agency last offseason to sign with his hometown Astros.

Williams, though, hasn't had nearly the same success in Houston that he did last season with the Padres. After finishing in the top 10 in the National League with a 3.65 ERA in 2006, the 40-year-old is 5-11 with a 5.03 ERA with the Astros.

While Williams does have an intimate knowledge of San Diego hitters after being in the Padres clubhouse the last two seasons, Black was quick to point out that pitchers don't always have the advantage when facing their former teams.

"I think it can work both ways," he said. "With players who have played this game a number of years, there are very few secrets. It comes down to execution."

Coming up: San Diego continues its four-game series in Houston on Saturday with the national FOX Game of the Week. Right-hander Greg Maddux (7-7, 4.11) takes the mound against Astros ace Roy Oswalt (9-6, 380). The first pitch is scheduled for 12:55 PT.