In the deal, Houston is sending three pitchers – Happ, Lyon, and David Carpenter – to Toronto in exchange for outfielder Ben Francisco, reliever Francisco Cordero, four Minor League prospects, and a player to be named later.

“This is a very good deal for us,” Astros General Manager Jeff Luhnow said in a release announcing the trade. “Once again we are adding depth to our minor league system with quality young players. We really feel this will help us moving forward and are extremely excited about the players we’ve added to our organization.”

The move is also a big boost for Toronto, as it adds to their bullpen and also bolsters a starting rotation beset by numerous injuries this season.

Happ, a 29-year-old lefty, was 7-9 with a 4.83 ERA in 18 starts this season for the Astros, and has gone 18-28 with a 4.84 ERA over the last two-plus years with Houston after a breakout 12-4, 2.93 performance with Philadelphia in 2009.

Lyon, meanwhile, has a 3.25 ERA in 37 relief appearances this year, and will be returning to the team for which he made his Major League debut (as a starter) in 2001.

Carpenter was 0-2 with a 6.07 ERA in 30 games with the Astros this year before being being reassigned to Triple-A Oklahoma City.

As for the Astros, their haul includes the 37-year-old Cordero, who was 3-5 with a 5.77 ERA in 41 games this season but is second only to Mariano Rivera in saves among active pitchers, and the 30-year-old Francisco, who was hitting .244 in limited playing time with the Jays.

But, as Luhnow alluded to, the key to the deal for Houston was the four Minor Leaguers acquired – three of which are pitchers, two of whom are former first-round picks.

RHP Joe Musgrove, 19, was selected in the compensation round of the 2011 Draft, and has made 11 career appearances (including eight starts) at the Rookie Level for both Bluefield and the GCL Jays over the last 14 months, going 1-1 with a 3.31 ERA.

RHP Asher Wojciehowski was selected in that same round in 2010, and the 23-year-old was 7-3 with a 3.57 ERA and 76 strikeouts in 18 starts for Class-A Dunedin this season.

The third pitcher, 22-year-old lefty David Rollins, was a 2011 pick and was 6-1 with a 2.78 ERA in 18 starts with the Class-A Lansing Lugnuts, and the fourth prospect is 21-year-old catcher Carlos Perez, who hit .269 with five homers, 40 RBI, and 21 doubles in Lansing this season.

Follow Lou DiPietro on Twitter: @LouDiPietroYES