Gonzalez joins a rotation that includes Stephen Strasburg and Jordan Zimmermann. Nationals general manager Mike Rizzo said the two clubs started talking about a Gonzalez trade about a month ago.
The trade talks between the two clubs escalated during the Winter Meetings after Washington was unable to acquire free-agent left-hander Mark Buehrle, who ended up signing with the Marlins. The trade for Gonzalez was finalized Thursday afternoon.
"We stepped up our efforts for a starting pitcher and the dialogue with the Oakland A's continued," Rizzo said during a conference call. "There was a momentum that we gained. Early on in the process, the asking price was much greater at the beginning then they were when you finish a deal, and that's the process of negotiating such a trade."
This past season, Gonzalez was 16-12 with a 3.12 ERA and had 197 strikeouts in 202 innings. He will not become a free agent until after the 2016 season. In Gonzalez, the Nationals add another left-hander to face sluggers such as Phillies second baseman Chase Utley and first baseman Ryan Howard.
"Being left-handed was really the key," Rizzo said. "We feel that he matches very nicely in between our two power right-handers in this division. It's important to have at least a couple of left-handers in the rotation and a couple of left-handers in the bullpen because of the talented left-handed hitting of players on the other teams.
"Gonzalez brings a presence in our rotation. He has had success. He has been a workhorse. He is very young. He just turned 26. He has accomplished a lot of things before his 26th birthday. It gives us a young core of starting pitchers at the Major League level that is in the realm of something that we never had here before. So we are really pleased to have him."
Rizzo is not concerned that Gonzalez is known to walk a lot of hitters. This past season, he walked 91 hitters. Rizzo believes the number will go down.
"We see his walks turning in the right direction," Rizzo said. "We see him having general command. We think as he progresses into his career, he is going to improve on his command. We see him turning in the right direction. He is a power left-hander that stacks up with the best in Major League Baseball. We thought it was very important for us to get a left-handed pitcher. We like the kid's stuff. We like his makeup a lot. We did a lot of work on this guy."
The Nationals traded three pitching prospects in Peacock, Milone and Cole, but the team still has pitching depth in the farm system. Matt Purke, Sammy Solis, Robbie Ray and Alex Meyer are considered top prospects.
"We feel that we are set up very well for the long haul," Rizzo said. "Don't forget, we have a Strasburg at 23, Gio Gonzalez at 26 and Zimmermann at 25. So they are young and not going anywhere. Our rotation is very young. We have a great depth behind them on the Major League level and a wave of pitchers coming and even a further wave after that."
Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the time He also could be found on Twitter @WashingNats. This story was not subject to the approval of Major League Baseball or its clubs.