If they detect a healthy beat, this is the time to bolster the roster for stretch runs, and hopefully postseason action, by leveraging also-ran teams' wishes to shed expiring contracts.
For most of the 20th century, the hump-day for pennant contenders was Sept. 1, when postseason rosters were frozen. The days leading up to that deadline were often marked by frenzied trading activity. In the post-1969 division era alone, the list of those who changed uniforms in the last few days of August reads like a Hall of Fame ballot: Don Sutton, Tommy John, Willie McCovey, Rickey Henderson, Lee Smith, Bill Madlock, Eric Davis and Tim Belcher.
Baseball's dramatic plotline was accelerated in the late 1980s, with the advent of the July 31 non-waiver trading deadline. Beyond that date, teams can now no longer deal players without first exposing them to waiver lists.
Although there continues to be considerable talk within the game about delaying this non-waiver trading deadline until at least mid-August, July 31 remains the ultimate fish-or-cut-bait day.
It's a focal point that invariably stirs up controversy and the emotions of people in the clubhouse and those who root for them.
You're damned if you do: Fans in rose-colored glasses do not take kindly to this very public waving of the white flag.
You're damned if you don't: Both fans of and players on contending teams itch for reinforcements, and rail if none are made.
There are never easy decisions. Does a contender stand pat? Do also-rans retain their nuclei or deal them for futures? What about teams on the bubble? Do they infuse new blood into a long shot? And the biggest variables through it all are veterans with expiring contracts, and teams' chances -- or desires -- to hold onto them.
Pre-trade deadline activity has altered the course of recent baseball history, both in the short term and the long term. For purposes of this retrospective, qualifying deals are those pulled between July 24 and July 31.
So here is our annual springboard into the summer trading season, a time of dog days and dog-eared rumors: A review of the good, the bad, and the did-we-really-do-that?
Most consequential deals
Cardinals got: Mark McGwire
Athletics got: Eric Ludwick, T.J. Mathews, Blake Stein
Although Oakland reaped a total of only six wins out of Ludwick and Stein, Mathews was a key cog in its bullpen for several years. But McGwire not only rewrote history in St. Louis, he remade his image. He will forever be thought of as a Cardinal, even though he had spent the first 11 1/2 seasons of his career by The Bay. The Cardinals were 51-54 when this deal was made and have been an NL Central powerhouse ever since.
Yankees got: Aaron Boone
Reds got: Brandon Claussen and Charlie Manning
Boone's presence in New York turned out to be fleeting, but not his impact. He took his permanent place in Yankees lore with the Game 7, 11th-inning home run that finished off Boston in the American League Championship Series. And until his unfortunate knee injury in a pickup basketball game, the thought of grabbing Alex Rodriguez hadn't even crossed GM Brian Cashman's mind.
White Sox got: Geoff Blum
Padres got: Ryan Meaux
Blum, now back in San Diego, turned into quite a loaner for Chicago. The White Sox certainly didn't need his help to reach the postseason -- they held a 13-game AL Central lead at the time of the deal. But Blum became huge in the World Series, with a 14th-inning homer in Game 3 that set up the sweep of Houston.
(A deferred prize; it takes many years to evaluate which way the scales tipped)
Yankees got: David Cone
Blue Jays got: Marty Janzen, Jason Jarvis, Mike Gordon
Cone went 9-2 the rest of that season, spearheading the Yankees' return to the postseason after a 15-year absence, and he went 51-24 the next four seasons, helping lay the foundation for the club's most recent dynasty. Janzen won a total of six Major League games; the other two players never appeared in a big-league uniform.
Tigers got: Damion Easley
Angels got: Greg Gohr
Easley enjoyed a considerable reign as a Motown star, driving in 100 runs in 1998 and totaling 69 homers in a three-year stretch. The right-handed Gohr logged a total of 24 innings for the Angels over the second half of that season, not to be seen in the Majors again.
White Sox got: McKay Christensen, John Snyder, Andrew Lorraine, Bill Simas
Angels got: Jim Abbott, Tim Fortugno
While the Pale Hose got a quartet of decent prospects -- Snyder won 16 games from 1998-99, and Simas gave them solid long relief for six years -- Abbott's return to Southern California was a disaster. He went 2-18 in 1996, then into retirement. Fortugno never made an appearance for the Angels before he, too, hung 'em up.
Do Unto Others Award
Mariners got: Jamie Moyer
Red Sox got: Darren Bragg
While Moyer has been one of baseball's biggest winners over the last eight years and is still going strong as a 40-something wonder, Bragg hit a total of 20 homers in 2 1/2 seasons in Boston, then walked as a free agent.
Red Sox got: Derek Lowe, Jason Varitek
Mariners got: Heathcliff Slocumb
The Sox got even with the Mariners good, picking up an entire battery in return for a reliever with a wonderful name and a woeful downside. Slocumb had 17 saves at the time of this deal, more than he would total the rest of his career.
Best way out
Mariners got: Carlos Guillen, Freddy Garcia, John Halama
Astros got: Randy Johnson
Angered when the Mariners declined to offer him a midseason contract extension, The Big Unit vowed to walk after the season. Performing coolly with this gun being held to his head, Seattle GM Woody Woodward engineered a wonderful deal.
Worst panic move
Phillies got: Placido Polanco, Bud Smith, Mike Timlin
Cardinals got: Scott Rolen, Doug Nickle
Rolen started his get-me-out-of-here diatribe in February, and then-Philadelphia GM Ed Wade strung out the market too long. He was cornered by St. Louis counterpart Walt Jocketty and did the best he could. Timlin was a two-month guest, Polanco has since gone on to Detroit and Smith never got well.
Mets got: Frank Viola
Twins got: Rick Aguilera, David West, Tim Drummond, Jack Savage, Kevin Tapani
What's that about the best trades helping both teams? Viola -- the first reigning Cy Young Award winner to be dealt -- was a 20-game winner for the Mets the following season. Minnesota got an entire mound set for its '91 World Series run -- starter (Tapani went 44-26 the next three seasons), setup man (West) and closer (Aguilera, who merely went on to post a franchise-record 293 saves).
Giants got: Sidney Ponson
Orioles got: Kurt Ainsworth, Damian Moss, Ryan Hannaman
A classic for a different reason -- both teams got burned. The Giants got three wins out of Ponson before he rode his free agency back to Baltimore. And a year later, the Birds still had a total of one win to show for the three pitchers they got, none of whom stayed with them beyond 2004.
Most controversial bail
Giants got: Wilson Alvarez, Danny Darwin, Roberto Hernandez
White Sox got: Lorenzo Barcelo, Mike Caruso, Keith Foulke, Bob Howry, Brian Manning, Ken Vining
The White Sox also got the business, from their fans, for unloading their ace and their closer when trailing AL Central-leading Cleveland by only three games. Club owner Jerry Reinsdorf hardly doused the flames by firing back, "Anyone who thinks this White Sox team will catch Cleveland is crazy."
Red Sox got: Orlando Cabrera, Doug Mientkiewicz
Cubs got: Nomar Garciaparra, Matt Murton
Expos/Nationals got: Brendan Harris, Alex Gonzalez, Francis Beltran
Twins got: Justin Jones
Accent on "temporary." None of those players suited up with his new team the following season until June, when the Nationals called up Harris, an infielder.
Biggest ado about nothing
A dizzying amount of activity broke out as the deadline approached -- a flurry of five deals involving 22 players. Like many storms, this one blew over quickly. The mostly forgotten names included Mike Jacobs, Dave Tuttle, Arnold Gooch, Jose Parra and both Marc and Mark Lewis.
Mike Stanton earned the unique distinction of being involved in deadline deals in consecutive seasons. In 1995, Atlanta dealt him and Matt Murray to the Red Sox for Jacobs and Marc Lewis. The next season, the Sox sent him with Dwayne Hosey to the Rangers in exchange for Mark Brandenburg and Kerry Lacy.
Travis Chick. The next box score he cracks will be his first, but this Chick must dig the long haul. On July 31, 2004, he went from Florida to San Diego in exchange for Ismael Valdes. A year later, he accompanied Justin Germano to the Reds for Joe Randa. Traveling Chick, more like it.
Other notable deadline deals
Harold Baines and Fred Manrique (White Sox) for Scott Fletcher, Sammy Sosa and Wilson Alvarez (Rangers)
Steve Karsay and Jose Herrera (Blue Jays) for Rickey Henderson (A's)
Brad Ausmus, Doug Bochtler and Andy Ashby (Rockies) for Bruce Hurst and Greg Harris (Padres)
Carlos Baerga and Alvaro Espinoza (Indians) for Jeff Kent and Jose Vizcaino (Mets)
Kirk Rueter and Tim Scott (Expos) for Mark Leiter (Giants)
Paul Spoljaric and Mike Timlin (Blue Jays) for Jose Cruz Jr. (Mariners)
Wilton Guerrero, Peter Bergeron, Jonathan Tucker and Ted Lilly (Dodgers) for Mark Grudzielanek, Carlos Perez and Hiram Bocachica (Expos)
Todd Stottlemyre and Royce Clayton (Cardinals) for Darren Oliver, Fernando Tatis and Mark Little (Rangers)
Jim Leyritz (Padres) for Geraldo Padua (Yankees)
Brian McRae, Rigo Beltran, Thomas Johnson (Mets) for Darryl Hamilton, Chuck McElroy (Rockies)
Jason Isringhausen, Greg McMichael (Mets) for Billy Taylor (A's)
Kevin Appier (Royals) for Blake Stein, Brad Rigby and Jeff D'Amico (A's)
Will Clark (Orioles) for Jose Leon (Cardinals)
Charles Johnson and Harold Baines (Orioles) for Brook Fordyce, Miguel Felix, Juan Figueroa and Jason Lakman (White Sox)
Melvin Mora, Mike Kinkade, Lesli Brea and Pat Gorman (Mets) for Mike Bordick (Orioles)
Ugueth Urbina (Expos) for Tomo Ohka, Rich Rundles (Red Sox)
Rick Reed (Mets) for Matt Lawton (Twins)
Jason Schmidt and John Vander Wal (Pirates) for Armando Rios and Ryan Vogelsong (Giants)
Fred McGriff (Devil Rays) for Manny Aybar and Jason Smith (Cubs)
Cliff Floyd (Expos) for Seung Jun Song and Sun Woo Kim (Red Sox)
Kenny Lofton (White Sox) for Felix Diaz and Ryan Meaux (Giants)
Ray Durham (White Sox) for Jon Adkins (A's)
Raul Mondesi (Yankees) for David Dellucci, Bret Prinz and Jon Sprowl (Diamondbacks)
Jose Guillen (Reds) for Aaron Harang, Joe Valentine and Jeff Bruksch (Athletics)
Scott Schoeneweis and Doug Nickle (Angels) for Gary Glover, Scott Dunn and Tim Bittner (White Sox)
Paul Lo Duca, Guillermo Mota and Juan Encarnacion (Dodgers) for Brad Penny, Hee-Seop Choi and Bill Murphy (Marlins)
Kris Benson and Jeff Keppinger (Pirates) for Ty Wigginton, Matt Peterson and Jose Bautista (Mets)
Victor Zambrano and Bartolome Fortunato (Devil Rays) for Scott Kazmir and Josellios Diaz (Mets)
Steve Finley and Brent Mayne (Diamondbacks) for Koyie Hill, Reggie Abercrombie and Bill Murphy (Dodgers)
Dave Roberts (Dodgers) for Henri Stanley (Red Sox)
Jose Contreras and cash (Yankees) for Esteban Loaiza (White Sox)
Shawn Chacon (Rockies) for Ramon Ramirez and Eduardo Sierra (Yankees)
Phil Nevin (Padres) for Chan Ho Park and $6 million (Rangers)
Kyle Farnsworth (Tigers) for Roman Colon and Zach Miner (Braves)
Bobby Abreu and Cory Lidle (Phillies) for C.J. Henry, Carlos Monasterios, Jesus Sanchez and Matt Smith (Phillies)
Carlos Lee and Nelson Cruz (Brewers) for Francisco Cordero, Kevin Mench, Laynce Nix and Julian Cordero (Rangers)
Austin Kearns, Felipe Lopez and Ryan Wagner (Reds) for Gary Majewski, Bill Bray, Royce Clayton, Brendan Harris and Daryl Thompson (Nationals)
Greg Maddux (Cubs) for Cesar Izturis (Dodgers)
Sean Casey (Pirates) for Brian Rogers (Tigers)
Bob Wickman (Indians) for Maximiliano Ramirez (Braves)
Mark Teixeira and Ron Mahay (Braves) for Jarrod Saltalamacchia, Elvis Andrus, Nefalti Feliz and Matt Harrison
Eric Gagne (Brewers) for Kason Gabbard, David Murphy and Engle Beltre (Red Sox)
Luis Castillo (Twins) for Dustin Martin and Drew Butera (Mets)
Ty Wigginton (Rays) for Dan Wheeler (Astros)
Scott Linebrink (Padres) for Joe Thatcher, Will Inman and Steve Garrison (Brewers)
Kenny Lofton (Rangers) for Max Ramirez (Indians)
Tadahito Iguchi (White Sox) for Michael Dubee (Phillies)
Scott Proctor (Yankees) for Wilson Betemit (Dodgers)
Matt Morris (Giants) for Rajai Davis (Pirates)