ST. LOUIS – St. Louis Cardinals pitcher Chris Carpenter’s rehab was put on hold after he injured his lower back in a bullpen session.

General Manager John Mozeliak said Thursday that any contribution this season from Carpenter, sidelined since February with nerve issues on the right side of his body, would be a bonus. But he said the prognosis has improved the last few days.

“We don’t think it’s as serious as we first thought,” Mozeliak said. “It’s slowing things down. Hopefully we can continue to work at it. As you can tell, we’ve got to be patient here.”

Before spring training, Carpenter, 38, and the team believed the injury might be career-ending. The 2005 NL Cy Young winner had been steadily progressing before the back tightened after he finished throwing Sunday.

Mozeliak anticipated the team would have a better handle on the situation after other doctors in St. Louis weighed in on the back issue. He said it was too soon to label starting pitching as a target at the trade deadline, and wasn’t ready to dangle top prospects as bait.

The Cardinals had the best record in the majors despite numerous pitching injuries. Jaime Garcia and closer Jason Motte are out for the year, and Jake Westbrook missed a month with a shoulder injury, but St. Louis has gotten big contributions from several rookie fill-ins.

“I don’t know what our needs will be on July 31,” Mozelilak said. “The good news is we’re playing pretty good baseball.”

PIRATES: Pittsburgh made a move to replenish its worn-out bullpen, calling up right-hander Duke Welker from Triple-A Indianapolis.

The Pirates optioned outfielder Alex Presley to Indianapolis to open a roster spot.

Welker was 3-1 with three saves and a 2.78 ERA in 25 games at Indianapolis.

Presley was called up for the second time June 8. He batted .293 in 17 games overall with two solo homers.

PHILLIES: While Philadelphia struggles to achieve even a winning record, speculation persists that pitchers Cliff Lee and Jonathan Papelbon will be available before next month’s non-waiver trade deadline. But that’s not necessarily the case.

“Absolutely not, because these are guys I’d be better off having on my club than not,” General Manager Ruben Amaro Jr. said. “Who am I going to replace these guys with to win a championship? These are championship-caliber players. If we think about moving these guys, then I better be getting someone of better or equal value and I just don’t see that happening.”

Lee, a 34-year-old left-hander, is 9-2 with a 2.53 ERA. He is signed for two more years at $25 million per plus a vesting option for 2016. He’s already been traded three times, including twice before the deadline.

Papelbon began the year 13 of 13 in save tries before blowing two chances during a three-game series against Washington. He’s signed for two more years at $13 million per plus a vesting option for 2016.

RANGERS: Texas plans to bring a top pitching prospect, Martin Perez, back to the majors and give ace Yu Darvish an extra day of rest.

The Rangers said they would recall left-hander Perez from Triple-A Round Rock on Saturday to start that night against St. Louis.

Rookie right-hander Nick Tepesch (3-6), who had been listed as Saturday’s starter, is being pushed back to the series finale Sunday of the team’s first trip to St. Louis since the 2011 World Series.

Darvish (7-3), the major league strikeout leader, had been scheduled to start Sunday night against Adam Wainwright (10-4). Darvish instead will pitch the series opener Tuesday at the New York Yankees.

METS: Jonathon Niese left his start against Atlanta in the fourth inning with left shoulder discomfort.

Niese winced as he finished making a pitch to Tyler Pastornicky with one out and motioned to the New York dugout that he was hurt.

David Aardsma replaced him with the Mets trailing 3-2.

Niese allowed eight hits and three runs in 31/3 innings, striking out five.