Buy or sell? National League trade outlook

This is the time of year that can make a difference between success and failure based on whether a Major League Baseball team buys, sells or holds firm on player transactions -- and there is no single set of rules to guide team executives.

The San Francisco Giants are evidence of how quickly tactics can change. The Giants won the 2012 World Series on the legs of two midseason acquisitions -- outfielder Hunter Pence and infielder Marco Scutaro.

Mere months later, vice president general manager Brian Sabean might be better off selling his assets, including Pence, to refocus the Giants' core for 2014.

Teams knocking on the door for a postseason spot are competing for the top arms on a crowded and expensive pitching market. Others, including the Pittsburgh Pirates, are shopping for budget buys.

Who are the buyers and sellers -- or others -- in the National League approaching the July 31 trade deadline? The Sports Xchange conducted a survey of its team correspondents for all 15 clubs to find out:

Arizona Diamondbacks -- Buyers.

Executive vice president Kevin Towers is known as a buyer. The Diamondbacks are kicking the tires in the pitching market, evaluating Milwaukee right-hand pitchers Yovani Gallardo of the Chicago Cubs as well as Jeff Samardzija and Jake Peavy of the Chicago White Sox. Right now, the asking prices are too high. Peavy makes $13 million this year and is due $14 million in 2014.

Colorado Rockies -- Holding for now.

Everything hinges on the result coming out of the All-Star break. The Rockies have a 10-game home stand against the Cubs, Marlins and Brewers. If it goes badly, the Rockies could become sellers and might listen to any offers for relievers Matt Belisle or Rafael Betancourt. Belisle, 33, has recovered from a slump in June, but his velocity is down this season, possibly because of his workload. Since 2010, Belisle has appeared in 273 games, more than other major league pitcher. Betancourt, 38, has returned from a groin injury that sidelined him for nearly all of June and has kept him from being as sharp as in past seasons. Belisle is making $4.1 million this season, and Betancourt's salary is $4.25 million. Both pitchers have a mutual option for $4.25 million in 2014 with a $250,000 buyout.

Los Angeles Dodgers -- Buyers.

The Dodgers already made their important move, sending three minor-league pitchers to the Miami Marlins for right-handed pitcher Ricky Nolasco. Nolasco gives the Dodgers depth in the starting rotation. They need similar boost in bullpen where Brandon League has lost the closer's job. Right-handed pitcher Carlos Marmol (acquired from the Chicago Cubs) could be a huge boost if he cleans up mechanics, command.

San Diego Padres -- Sellers.

The Padres likely went from buyers to sellers during their 4-18 plunge heading into the break. Right-handed starting pitchers Edinson Volquez and Jason Marquis are the two most likely to go, but both have slumped. Volquez drew up to 10 scouts at recent starts and is a free agent at the end of the season. But scouts saw Volquez give up 12 runs on 17 hits and five walks over 10 1/3 innings in his last two starts.

San Francisco Giants -- Sellers.

This will measure the, ah, intestinal fortitude of general manager Brian Sabean. Noted as a buyer during 2010 and 2012 championship seasons, Sabean may need to sell some fan favorites on the Giants' record. Tim Lincecum, whose last start before the break was a no-hitter in San Diego, and right fielder Hunter Pence can be free agents and could be dealt for younger, cheaper players who'd complement next year's core. Bottom line is that Lincecum is making $22 million, Pence $13.8 million and neither will be cheap to retain.

Chicago Cubs -- Sellers.

They already traded veteran players for prospects and international signing-bonus money. The selloff should continue right to the July 31 non-waiver deadline and beyond. Starting pitcher Matt Garza is the prime candidate to be traded. He ended the first half 6-1 with a 3.17 ERA, and for the most part, he was dominant, but could be a free agent. Team president Theo Epstein: "There are teams out there looking for pitching who have called trying to acquire him." Closer Kevin Gregg and RF Nate Schierholtz are the other most-talked-about trade targets.

Cincinnati Reds -- Buyers.

Here's the question: What to buy? "It depends on what week," general manager Walt Jocketty said. First the bullpen looked like a big need, but it has stabilized with a record 32 2/3-inning scoreless streak. A right-handed bat is probably the No. 1 need entering the second half. But Chris Heisey has hit well (9-for-27, five doubles, two home runs) since coming off the disabled list, so there's a chance the Reds won't make a major deal.

Milwaukee Brewers -- Sellers.

As residents at the bottom of the NL Central, the Brewers are sellers but two of their bigger trade chips came off the table when 1B Corey Hart (knee) was lost for the year and 3B Aramis Ramirez was compromised by a sprained knee. Teams are interested in the Brewers' bullpen pieces, including John Axford, Francisco Rodriguez and Michael Gonzalez. The last two of whom will be free agents after the season.

Pittsburgh Pirates -- Buyers.

Buyers at the last two non-waiver deadlines, and in better position to reach the postseason this time, the Pirates could use a power bat, preferably in right field or maybe at first base. Strengthening the rotation isn't as great a priority but it wouldn't hurt to add depth because left-handed pitcher Wandy Rodriguez, the No. 2 starter, has been sidelined since June 6 with forearm stiffness.

St. Louis Cardinals -- Sellers turned buyers.

The Cardinals trimmed dead wood, releasing veteran infielder Ty Wigginton and trading struggling reliever Mitchell Boggs (Triple A Memphis). Like most, the Cardinals are looking pitching help, a starter and/or a veteran right-handed reliever -- dependent on 38-year-old Chris Carpenter, who is in the midst of another comeback. St. Louis is asked about top young players -- pitchers Michael Wacha or Carlos Martinez; or their top minor-league hitters like second baseman Kolten Wong and outfielder Oscar Taveras. But the Cardinals won't deal top-shelf prospects for rentals.

Atlanta Braves -- Buyers.

The Braves will be on the lookout for help in the bullpen and somebody or two to add to a weak bench. There is money left in the 2013 budget despite a busy offseason. An experienced reliever to complement closer Craig Kimbrel and a veteran addition to the bench could be the difference from just making the playoffs and being a real postseason threat.

Miami Marlins -- Listening.

The Marlins did their heavy lifting July 6 by trading pitcher Ricky Nolasco to the Los Angeles Dodgers for three pitching prospects. While the Marlins continue to listen to offers for other players, they are not actively shopping anyone else. "We have a lot of good young players that people are interested in, but we're interested in them also," baseball operations president Larry Beinfest said. Among players getting interest from other teams: slugger Giancarlo Stanton and relievers Steve Cishek, Mike Dunn, Chad Qualls and Ryan Webb.

New York Mets -- Mixed.

The Mets have a glut of pitching prospects on the farm and could seek to package some of them for the type of young, controllable outfielder their lineup has been missing. Or they could sell off any pending free agents who have some value, such as OF Marlon Byrd or C John Buck. Their most desirable chip may be right-handed pitcher Bobby Parnell, who is under team control for two more years, but the Mets have already publicly expressed reluctance to deal their closer.

Philadelphia Phillies -- Mixed.

The Phillies played themselves into no-man's-land at the trade deadline. They are too close to the top of the NL East and the second wild card to completely give up, but are lacking players in the minor leagues necessary to help fill major holes. The injury to Ben Revere forced Ruben Amaro Jr. to look for centerfield options. Things could change quickly, when the club's three potential free agents -- Chase Utley, Michael Young and Carlos Ruiz -- are likely to be shopped along with closer Jonathan Papelbon, who could be appealing to the Tigers and Red Sox.

Washington Nationals -- Holding for now.

General Manager Mike Rizzo said at the beginning of the season he felt his 25-man roster stacked up with any in the league. But the offense flopped in the first half due to a few factors, including leadoff hitter Denard Span's inconsistency, injuries to top hitters and the struggles of second-baseman Danny Espinosa, who has been rehabbing at Triple-A Syracuse. Bryce Harper, Jayson Werth, Wilson Ramos and Ryan Zimmerman missed 131 combined games due to injuries. Rizzo believes with all four position players healthy and back in the lineup the offense will improve. Rizzo added veteran Scott Hairston right before the break to shore up a bench that has been ineffective. If Espinosa gets hot, Rizzo could move the second baseman for pitching or more depth before the trading deadline.