Marcus Stroman became the first big name to move, followed by Trevor Bauer -- and then the Astros landed Zack Greinke in a last-minute blockbuster. Here are the moves that went down before the 4 p.m. ET deadline on July 31, along with analysis of what these transactions mean for the teams that made them.
Trade deadline reaction
Winners and losers of an unexpectedly wild deadline. Here's who scored (hint: the Astros!) and struck out (sorry, Yankees) when the dust settled. David Schoenfield
Completed MLB trade tracker
July 31 deals
Astros get Zack Greinke in late blockbuster deal! Just when it looked like this deadline would go quietly, Houston sent shockwaves through baseball by acquiring Zack Greinke from Arizona. The Diamondbacks are getting four prospects for Greinke, a source tells ESPN.
Passan: Astros took steps for 2nd World Series in 3 years
Keith Law and Jeff Passan detail the Astros' moves in acquiring Zack Greinke, Joe Biagini and Aaron Sanchez.
Our one-sentence take: The Giants get a modest improvement to their offense as they try to make a wild-card run in Bruce Bochy's final year as manager.
Our one-sentence take: The 27-year-old can be slotted in at multiple spots on the diamond and should provide a big boost offensively to a Chicago team that entered Wednesday's action a game behind the first-place Cardinals in the NL Central and atop the wild-card standings.
Braves get a big bullpen boost: The Atlanta Braves improved their relief corps before the trade deadline by acquiring All-Star closer Shane Greene from the Detroit Tigers. Atlanta followed the Greene addition with a deal with San Francisco for reliever Mark Melancon.
Dodgers add to offensive depth: The Dodgers acquired infielder Jedd Gyorko in a trade with the Cardinals. The 30-year-old has power, can play multiple positions and provides insurance given the injuries to Chris Taylor, Enrique Hernandez and David Freese.
Phillies add veteran bat: Outfielder Corey Dickerson has been traded to Philadelphia from Pittsburgh, according to ESPN's Jeff Passan. Dickerson is hitting .300 with four homers and 25 RBIs this season. He hit a career-high 27 dingers for the Rays in 2017.
A rare prospect trade at the deadline: July 31 trades are usually about an immediate fix for at least one side involved in the deal, but the Marlins and D-backs made a trade of prospects that is all about the future for both. Zac Gallen is headed to Arizona for shortstop prospect Jazz Chisholm, a source tells ESPN. Gallen has been very good, with a 2.72 ERA in seven major league starts.
Law: Marlins betting big on upside of Chisholm
Keith Law contends that the Marlins are betting on Jazz Chisholm's upside after acquiring him from the Diamondbacks.
The deal: A's acquire Tanner Roark from the Reds.
Our one-sentence take: The A's get some quality depth for their wild-card push while Cincinnati moves a free-agent-to-be who became even more expendable when the Reds added Trevor Bauer to the top of their rotation.
Our one-sentence take: Look, the Nats really needed to address their bullpen and adding two of Seattle's best relievers along with Daniel Hudson (see below) is a positive step there.
Our one-sentence take: Washington adds a veteran arm to a bullpen lacking in quality late-game options.
Our one-sentence take: The move creates flexibility as the Cubs continue to look to improve either their starting lineup or their bench while Houston reunites with a catcher who finished last season as an Astro.
Our one-sentence take: Tampa Bay is betting that a 2018 All-Star can return to last year's form as a power bat while Milwaukee adds a versatile arm.
July 30 deals
The deal: The Reds acquired Trevor Bauer, The Indians acquired Yasiel Puig, Franmil Reyes and more, and the Reds acquired prospect Taylor Trammell.
Our one-sentence take: This is the blockbuster we've all been waiting for with the Reds making a surprising play for an ace, the Indians adding two powerful outfielders and the Padres jumping in at the chance to grab an elite outfield prospect.
Passan: Brewers, A's are making incremental upgrades
Jeff Passan and Keith Law express how the Brewers adding Jake Faria and the Athletics' addition of Jake Diekman upgrades their rosters.
The deal: The Rangers send right-handed reliever Chris Martin to the Braves for LHP Kolby Allard.
Our one-sentence take: Using the organization's prospect depth to get bullpen help might sound good in principle, but trading away Allard, -- the No. 14 prospect in the organization in Keith Law's pre-season ranking -- for a 33-year-old journeyman enjoying his first significant big-league success, feels like a steep price to pay.
Our one-sentence take: The Cubs add a veteran arm to a bullpen in desperate need of quality depth.
Our one-sentence take: With Jake Arrieta ailing, the Phillies needed an arm and got a decent one in Vargas, whose departure lets the Mets shed about $2 million in salary they can spend elsewhere this year or next.
The deal: The Brewers acquire right-hander Jordan Lyles from the Pirates for pitching prospect Cody Ponce. (July 29)
Our one-sentence take: The Brewers definitely needed some rotation help, but it's hard to see Lyles (9.58 ERA in eight starts since the end of May) as the answer.
The deal: The Mets acquire veteran right-hander Marcus Stroman from the Blue Jays for pitching prospects Anthony Kay and Simeon Woods Richardson. (July 28)
Our one-sentence take: Stroman is a solid starter having one of his best seasons, but the Mets aren't close enough to contending to trade two of their top 10 prospects for short-term help.
The deal: The Rays acquire veteran infielder Eric Sogard from the Blue Jays for two players to be named later. (July 28)
Our one-sentence take: Hitting .300/.363/.477 with Toronto, Sogard is a nice pickup, giving Rays manager Kevin Cash some versatility and another option at second base and could be one of those under-the-radar deals that proves to be a key acquisition.
The deal: The Indians acquired infielder Christian Arroyo and pitcher Hunter Wood from the Rays for minor league outfielder Ruben Cardenas and international slot money. (July 28)
Our one-sentence take: A small trade, but a nice depth move for the Indians as Arroyo, who was hitting .314/.381/.603 in 33 games at Triple-A, provides a backup infield option, and Wood (2.48 ERA in 29 innings) provides more depth for a bullpen that has the best ERA in the majors, while the Rays solve their 40-man roster jam.
The deal: The Twins get right-handed reliever Sergio Romo (plus prospect Chris Vallimont and a PTBNL) from the Marlins for Double-A first baseman Lewin Diaz. (July 27)
Our one-sentence take: Romo's a veteran reliever with three rings (with the Giants) and experience closing, setting up and doing whatever's needed, so he'll give the Twins pen everything it could ask for down the stretch.
Our one-sentence take: A's add a power southpaw to shore up their pen and their wild-card bid, apparently without touching their 40-man roster.
Our one-sentence take: The deal gives the Cubs an insurance policy behind the plate for the stretch, as it comes on the heels of their having to put starting catcher Willson Contreras on the IL briefly with a strained foot.
The deal: Athletics get Homer Bailey from Royals (July 14)
Our one-sentence take: As they make their midseason surge up the standings, the Athletics added an under-the-radar starter having his best season in five years.
The deal: Red Sox get Andrew Cashner from Orioles (July 13)
Our one-sentence take: With Nathan Eovaldi ticketed for a bullpen role upon his return from the injured list, the Red Sox turned their attention to the rotation and added a veteran with American League East experience, in Cashner.
The worst deadline trade ever for all 30 teams
Curt Schilling (twice!), Corey Kluber and "What the hell did you trade Jay Buhner for?!?" We relive the summer blockbusters gone wrong that GMs everywhere would love to forget. David Schoenfield
What front offices are saying
"We really don't have any holes right now. If we stay healthy, this team is as good as any team I've ever seen." Astros general manager Jeff Luhnow on adding Zack Greinke
Brodie Van Wagenen on Mets' addition of Marcus Stroman: "Marcus is a dynamic talent who will bring tremendous passion to our team and energy our fans will truly appreciate. As a Long Island native, we believe that Marcus will thrive playing in New York."
Mike Rizzo on Nats' deadline moves: "These guys are all qualified to pitch the seventh, eighth, and the ninth inning. They all have saves on their resume, and they're all stuff guys that can get big outs at big times. The role system, I think that'll kind of work itself out. We're just kind of getting our arms around the new acquisitions and see where it falls amongst the way we'll rotate them in the bullpen."
Farhan Zaidi on decision to keep Madison Bumgarner: 'When he's on your side, you always feel like you have a chance'
Jed Hoyer on Cubs' addition of Nick Castellanos: "When you watched us play over the last few months, it felt, at times, we were a bat short in the lineup. He kills lefties. That's something we've really struggled with. We think he's going to give a pro at-bat versus righties and lefties."
Brian Cashman on Yankees' inactivity at the deadline: "The best play was we did nothing. And we did nothing for a very good reason, because we felt everything that was in front of me was really not obtainable because of the associated costs,"
Andrew Friedman on the Dodgers' attempts to make a deadline splash: "I don't think this is something where we were looking to win a deal from a value standpoint. You kind of expect in July not to do that. We made plenty of offers that were definitely under water from a value standpoint but felt good about making because of the pieces that we have."