HOUSTON -- Astros shortstop Jed Lowrie, who's been on the disabled list since July 15 with a sprained right ankle and an injury to the peroneal nerve in his leg, said Thursday he's confident he'll return to action at some point this season.

Lowrie has been undergoing daily rehab in Houston and has been wearing a brace to limit the mobility in his knee, though it's getting better. While the ankle has healed, Lowrie has a ways to go before being game ready. He was examined by a doctor Wednesday.

"I think it will certainly be by the end of the year, and as far as when specifically, I think it's a moving target just because it's a really atypical injury and there's not a lot of precedent on a hard timeline," he said. "I think would make it a lot easier if there were, but there's not."

Lowrie has been taking his rehab slowly, beginning with just an hour a day before progressing to more intense reps on his leg to make it stronger.

"I guess I'm pretty optimistic, so I always thought that there was going to be an opportunity to come back this year, but I don't know what internally they're saying about it," he said. "I always felt like with no structural damage, and since it happened only a couple of days after the All-Star break, I had time to get it right and play the last few weeks of the season."

Outfield prospect Springer elevated to Double-A

HOUSTON -- George Springer, the Astros' top pick in the 2011 First-Year Player Draft, was promoted to Double-A Corpus Christi on Thursday. Springer, an outfielder, hit .316 with 10 triples, 22 homers, 82 RBIs and 28 stolen bases at Class A Lancaster.

The Astros are expected to promote a few more players within in the next week to see how they perform at a higher level for the final few weeks of the Minor League season, general manager Jeff Luhnow said.

"We're going to place prospects at the level we think they need to get accustomed to for next year," Luhnow said. "That will put us in a good spot for the remainder of the year."

Springer is one of the reasons the Astros' farm system is now considered on the rise. The farm system has improved considerably the last two years through trades and the Draft.

Houston's top four Minor League clubs had a combined record of 255-210 (.548) entering Thursday, which is the most drastic improvement of any organization from 2011 to 2012. Luhnow said he wants to make moves that won't jeopardize the clubs' chances of winning a title.

"We do need to be cognizant of not stripping a team of what's making it successful so far this year," Luhnow said. "We also want guys to have an opportunity to experience what it's like to win a championship in the Minor Leagues. I have six Minor League rings from my time in St. Louis, and I want to start accumulating those here as well.

"It creates an attitude, an expectation, a mindset that's healthy for the whole organization. These guys come up and they have a chance to win together. It makes a big difference in how they start here."

Crane pleased with improvements in Minors

HOUSTON -- Having recently returned from a trip to the Olympic Games in London, Astros owner Jim Crane took time Thursday to address reporters at Minute Maid Park about the state of the club. Crane remains steadfast that the club is on the right track despite its on-field struggles.

Crane believes players are feeling some pressure and simply need to relax.

"We're just looking for a spark to get over the edge," he said. "It's been very tough for everybody. We'd like to get a couple of wins under our belts, but we made a lot of trades and once we made that decision [to trade veterans] and get started moving in that direction, we knew we might slide back a little bit, but we weren't hoping it would be this bad."

The Astros have made six trades since the start of July, dealing players like Carlos Lee, Brett Myers, Wandy Rodriguez, J.A. Happ and Chris Johnson in exchange for prospects. Crane is pleased with how much the Minor League system has improved.

"I think we did the best we could in trying to shore up with the trades," he said. "We got about 15 players and hopefully some of our prospects look very good. We're sticking with the plan. We told you we were going to work that way, build up the Minor League system. Some of the reports I've seen said the system's gone from last to somewhere around 10th, so hopefully we'll see that continue to improve."

Crane said no decisions have been regarding any changes in the coaching staff for next season, saying general manager Jeff Luhnow will assess the situation at the end of the season. The owner said there will be upgrades to the Diamond Club seats next year, and he said fans will have a say in whether Tal's Hill and the locomotive above left field return for 2013 -- Houston's first season in the American League.