The Boston Red Sox and Atlanta Braves both made additions to their squads before the non-waiver trade deadline passes.
The American League East-leading Red Sox landed three-time All-Star and 2003 Cy Young Award winner Eric Gagne from the Texas Rangers in exchange for three young players, including left-hander Kason Gabbard.
Meanwhile, the Braves finalised their second deadline deal when they got Octavio Dotel from the Kansas City Royals for Kyle Davies.
Earlier, the Braves announced the acquisition of first baseman Mark Teixeira from the Rangers in a six-player swap which included catcher Jarrod Saltalamacchia.
Gagne was 2-0 with a 2.16 ERA and 16 saves for the Rangers this season.
He goes to Boston as a setup man for closer Jonathan Papelbon.
The former Los Angeles Dodger had the right to veto a trade but elected to go to Boston, where the Red Sox led their division by eight games.
"We're excited," Red Sox general manager Theo Epstein said.
"We feel like we have a really good club. We were looking for ways to strengthen it, and I think the bullpen is clearly a strength of the club. Acquiring a pitcher the caliber of Eric Gagne only makes us stronger."
The Braves trailed the New York Mets by four games in the National League East, but have a vastly improved side after adding Teixeira and Dotel.
Teixeira is a premier power hitter and ace fielder, while Dotel saved 11 games for Kansas City this season and will be used as a setup man for closer Bob Wickman.
"It makes us a real World Series contender," said Braves right fielder Jeff Francoeur.
The San Diego Padres, a half-game out of first place in the NL West, picked up third baseman Morgan Ensberg, utility player Rob Mackowiak and lefty Will Ledezma in three separate deals.
Lots of business
In other deals, the Yankees took infielder Wilson Betemit from the Dodgers in exchange for reliever Scott Proctor; the Pittsburgh Pirates acquired veteran right-hander Matt Morris from the San Francisco Giants for outfielder Rajai Davis and a player to be named; the Philadelphia Phillies landed right-hander Julio Mateo from the Seattle Mariners; and the St. Louis Cardinals picked up right-hander Joel Pineiro from the Red Sox.
With Tuesday's deadline passed, players have to go through waivers to be traded, making deals more difficult.