ST. LOUIS -- Four Astros Minor League players have been suspended 50 games after testing positive for a performance-enhancing substance in violation of the Minor League Drug Prevention and Treatment Program.

Assistant general manager Ricky Bennett said right-hander Danny Meszaros (Triple-A Round Rock), catcher Jonathon Fixler (Double-A Corpus Christi) and shortstop Marcos Cabral (Corpus Christi) have been suspended.

Earlier Wednesday, Major League Baseball announced pitcher Richard Rodriguez of the Astros' Dominican Summer League team had been suspended.

Meszaros, who advanced to Triple-A after being drafted in the 48th round in 2008, was 2-1 with a 5.40 ERA in seven games at Round Rock after going 3-1 with a 3.09 ERA in 26 games at Double-A Corpus Christi to start the year. Fixler was hitting a combined .242 with six homers and 22 RBIs between Corpus Christi and Class A Lexington, and Cabral was hitting .259 with five homers and 24 RBIs between Round Rock and Corpus Christi.

"The Houston Astros fully support the efforts of the Commissioner's Office to rid our sport of any type of inappropriate drug use," Astros general manager Ed Wade said in a statement. "Our players and staff have been briefed, counseled, educated and warned about what the ramifications and consequences are when they choose, either knowingly or not, to violate the MLB drug policy. And yet, despite the best efforts of MLB and the Astros, we still have individuals who abuse our game by ignoring reality. We are embarrassed by these types of suspensions. They are a smear on our game and our organization, and we will redouble our efforts to make sure the message gets through."

Moehler suffers rehab setback

ST. LOUIS -- Right-hander Brian Moehler suffered a setback in his rehabilitation from a groin injury Wednesday afternoon when he felt a popping sensation in the area while pitching a simulated game. He made it through 38 of his scheduled 45 pitches before feeling the discomfort.

Moehler, who has been on the disabled list since July 8 with a right groin strain, flew back to Houston on Wednesday night and will undergo an MRI on Thursday. Moehler was clearly frustrated as he packed his bags for an unexpected flight to Texas.

"I don't know what to think," he said. "I can't imagine it's good news. I heard a pop. It had felt great. It's the best I felt in over a month. I threw one pitch and just felt it. You know what? There's nothing I can do about it. We'll get it checked out."

Moehler, 38, is 1-4 with a 4.92 ERA in 20 games, including eight starts. Astros manager Brad Mills was encouraged with the way Moehler was pitching to hitters before he aggravated the injury.

"It was really too bad because he felt so good going in," Mills said. "The first inning he went through the sim game, he threw the ball really well and felt good and then went out for the second inning and then halfway through it started bothering him again. That definitely is a disappointment and a concern."

Manzella set to begin rehab assignment

ST. LOUIS -- Rookie shortstop Tommy Manzella, who's been out six weeks with a fractured left index finger, is scheduled to begin his Minor League rehab assignment Thursday night in Corpus Christi. Manzella flew to Houston from St. Louis on Wednesday night and will undergo a precautionary MRI before joining the Hooks.

Manzella gave the finger a good test when he participated in a simulated game Wednesday and faced teammate Brian Moehler.

"On the swings I took off Moe I felt pretty good," he said. "I had one where I kind of foul-tipped it and didn't square it up and that was good and I responded well to that. I'm definitely ready to get going and get into a game."

The plan is for Manzella to get two at-bats in two games and then increase to three at-bats in two games. When he's prepared to play a full game, he will continue his rehab at Triple-A Round Rock. The longest the rehab could last is 20 days, but Manzella hopes it won't be that long.

"It's going to depend on how I feel," he said. "I think it's going to be on my end, basically getting into playing shape and letting them know when I'm physically ready to play."

Bagwell humble as Astros' bats heat up

ST. LOUIS -- Prior to Wednesday's game, the Astros were ranked second in the National League with a .284 batting average in the second half of the season. They were averaging 5.9 runs per game in the second half, after hitting .238 and averaging 3.5 runs in the first half.

"They have the talent, and it's just one of those things it's taken longer than we'd hoped, but guys are working hard every single day," said hitting coach Jeff Bagwell, who took over at the All-Star break. "Trust me, it's all them."

Bagwell was part of quite a few huge offensive outbursts during his 15 years as a player with the Astros, but he took great pride in watching the Astros explode for a season-high 18 runs and 22 hits in Tuesday's blowout win over the Cardinals.

"It was good and I was happy for the guys," Bagwell said. "Any time you have success, that always breeds confidence. Hopefully last night some of the guys are able to take a lot out of that. It's fun to get hits like that. It doesn't happen all that often, so when it does you have to enjoy it."

Worth noting

Right-hander Felipe Paulino, on the 60-day disabled list with right shoulder tendinitis, will go for a second opinion on his shoulder next week. "He hasn't responded like he had hoped or we had hoped," manager Brad Mills said. ... Boxing promoter Don King threw out the first pitch Wednesday.