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The St. Louis Cardinals at spring training in Jupiter, Fla.

Cardinals general manager John Mozeliak insists that the best way to improve the offense is to get a return to form from the stalwarts. (Chris Lee clee@post-dispatch.com)

SAN DIEGO • The next time the Cardinals will need a fifth starter is Saturday against first-place Milwaukee, and though the series is on the horizon manager Mike Matheny said the club is keeping the spot open for now because of who could fill it.

That pitcher may be currently with another team.

As Thursday afternoon’s trade deadline approaches, the Cardinals are in conversations with several teams for starting pitchers, and Matheny acknowledged Tuesday that those pursuits could influence or answer who starts Saturday at Busch Stadium.

“I think there’s always the possibility (that) anything could happen,” Matheny said before the Cardinals’ late game against San Diego at Petco Park. “We’re talking about the fifth spot we have open. We could look at what happens to our bullpen, how we use guys. But this all comes down if anything happens externally. There are a lot of things that go into play.”

The Cardinals have had contact with Tampa Bay about its ace David Price, the prize of this trade market, and the Cardinals have not shown any apprehension over the high cost of prospects it would take to land Price. It could take a top prospect like Oscar Taveras, a talent the Cardinals have previously described as too elite to trade.

Reports indicated Monday that the Phillies would entertain offers for several of their starting pitchers, including lefty Cole Hamels and veteran righty A.J. Burnett. The Phillies dispatched a scout to see the Cardinals’ Class AAA affiliate Memphis play at Omaha on Tuesday night. Tyler Lyons pitched a four-hitter, while outfielder Stephen Piscotty is viewed as one of the most attractive prospects at that level.

Hamels pitched eight scoreless innings for the Phillies on Tuesday night; Burnett, the easier of the two to acquire at the deadline, is next scheduled to start Saturday for Philadelphia.

Cardinals general manager John Mozeliak and several members of his brain trust, including assistant general manager Michael Girsch and director of player personnel Matt Slater, have joined the team in San Diego for the hours before the non-waiver trade deadline. After Thursday players must clear waivers before being traded.

Mozeliak has stated several times this past week that pitching is a target.

The market has an assortment of options at starter. The Boston Red Sox scratched lefty Jon Lester from his scheduled start today. He is signed through the remainder of this season, and the Cardinals have previously expressed a reluctance to part with a top-tier prospect for a rental. The Cardinals also have a competitive-balance draft pick to trade, and in a deal for Lester that would give Boston close to the equivalent of the compensation pick they'd get by holding on to Lester and he signs with another team this winter. The small chance of re-signing Lester and the fact traded players are no longer eligible for the compensation draft pick makes him less attractive that pitchers with more control.

It has been a seller's market given the prices already paid for pitching.

Cleveland is open to moving Justin Masterson, Yahoo! Sports reported. Like Lester, Masterson is a pending free agent and would not net a new team a compensation pick if signed by another team this winter.

San Diego’s Ian Kennedy, scratched from a start Monday with an oblique injury, is scheduled to throw a bullpen session today to prove his readiness for a start this weekend, though The San Diego Union-Tribune pegged his likelihood of being traded at “50-50.” Like Price, Kennedy has another year of team control.

Hamels has $96 million remaining on his contract, which includes the $6 million buyout on the option for 2019. The Cardinals are one of the teams to which Hamels cannot block a trade.

Like other Phillies, Burnett has an expensive option tagged to his contract, one that could increase to an $11.75 million player option with 30 starts, according to reports.

While the front office scans for options, Matheny said there are internal candidates to make the start Saturday. Carlos Martinez could emerge from the bullpen to start, though his use in this series against San Diego would change that. The other option is promoting a starter from Class AAA Memphis. Lyons would be unavailable.

He said the clubhouse has not been preoccupied with the trade talk.

“I think our guys have done a nice job of not falling into the trap of being a vocal junior GM,” Matheny said. “That’s a bad spot to be in. That’s a bad spot for the players to go to. Where they’re starting to use their voice to try and push without having all of the information. It’s not a smart move. You start taking about clubhouse dynamics and you’re basically telling somebody in there that they’re not doing their job. I don’t think it’s a great plan.”

Matheny declined to say where he thought the Cardinals could improve.

In truth, their actions already show it.

The team has increasingly said the offensive upgrade is going to have to come from the roster they already have, while they started the second half with four starters. Their use of the roster implies an opening they intend to fill, if possible by Thursday to be ready for Saturday. They have a spot waiting for a newcomer.

“We’re doing things behind closed doors trying to make our team better,” Matheny said. Not making a move “is something that we have to keep in mind. You can have the most perfect laid out game plan on how you can improve this club. There are a lot of different things that have to happen for that to work. There is a high likelihood that who you have is who you are going to be.”

EXTRA BASES

Cardinals ace Adam Wainwright joined Twitter on Tuesday, encouraged by family and inspired by the need to promote his ever-expanding fantasy football-as-charity initiative. Wainwright picked the Twitter handle @unclecharlie50, merging the nickname for his signature curveball with his jersey number. ... The Cardinals asked for release waivers on catcher George Kottaras for the purpose of removing him from the 40-man roster and allowing him to leave the organization. Briefly the Cardinals’ backup catcher, Kottaras was designated for assignment Saturday to make room for newcomer A.J. Pierzynski, who started his third straight game Tuesday night. … Former Cardinals pitcher Jason Simontacchi, who now serves the organization as Low-A Peoria’s pitching coach, will represent the organization as a pitching coach at the Arizona Fall League. Simontacchi will coach for the Peoria affiliate in the invitation-only league for elite prospects. … Before Tuesday’s game, the Padres activated shortstop Everth Cabrera off the disabled list, where he had missed 20 games with a hamstring strain. … The Cardinals held the draft order drawing for their annual fantasy football league, and bench coach Mike Aldrete claimed the rights to the first overall pick.

Derrick Goold is the lead Cardinals beat writer for the St. Louis Post-Dispatch and past president of the Baseball Writers' Association of America.