Never before this week had a general manager of the Washington Nationals been in position to make a trade that could legitimately put the franchise on the cusp of contender status, a heady reality that colored Mike Rizzo’s acquisition of all-star left-hander Gio Gonzalez from the Oakland Athletics on Thursday.

“I feel good, I feel optimistic about where we’re at,” Rizzo said in a conference call with reporters Friday night, after the Gonzalez trade became official. “Our goal is to be playing meaningful games at the end of the season and beyond.”

Rizzo spoke like the GM of a borderline contender, the kind of team that would give up four top prospects — pitchers A.J. Cole, Tom Milone and Brad Peacock, and catcher Derek Norris — for one established front-line starter, the 26-year-old Gonzalez, and a throw-in, 24-year-old Class A pitching prospect Robert Gilliam. For much of the franchise’s seven-year stay in Washington, the Nationals were more likely to be on the other end of such a trade.

“This gives us a core of pitchers at the major league level,” Rizzo said, “that is in the realm of something we’ve never had here before.”

Rizzo said the Nationals and A’s first began discussing a Gonzalez deal more than a month ago, with the talks heating up at the winter meetings earlier this month, cooling slightly as the Nationals made a run at free agent lefty Mark Buehrle, then heating up again when Buehrle chose the Florida Marlins.

“He’s a power left-handed pitcher that stacks up with the best in Major League Baseball,” Rizzo said of Gonzalez. “We like the kid’s stuff, [and] we like his makeup a lot. We’ve done a lot of work on this guy…. He’s an awesome competitor. I call him – in a good way – a sore loser. He has moxie and attitude on the mound that we like.”

While the longtime scout in Rizzo bemoaned the “painful” cost in homegrown prospects that it took to land Gonzalez, the front-office executive in him was practically giddy at the thought of slotting Gonzalez — a pitcher Rizzo has coveted since seeing him pitch as a high schooler in Miami — in between right-handers Stephen Strasburg and Jordan Zimmermann atop the Nationals’ rotation.

“We feel he matches up very well between our two power right-handers,” Rizzo said. “We think in [the NL East] it’s important to have at least a couple of left-handers in the rotation and at least a couple of left-handers in the bullpen, because of all the talented left-handed hitters on other teams. [Gonzalez] brings a presence in our rotation….

“We feel we’re set up very, very well for the long haul. With Strasburg at 23, Gio Gonzalez at 26 and Zimmermann at 25 — those guys are young. They’re not going anywhere. Our core rotation is very, very young.”

Looking beyond the first three spots in the 2012 rotation, Rizzo sees right-hander Chien-Ming Wang and lefties John Lannan and Ross Detwiler competing for the two remaining positions, with the loser conceivably heading to the bullpen.

With many in the industry speculating the Nationals could still make a late, stealth run at free agent slugger Prince Fielder — which, theoretically at least, would cement their status as 2012 contenders — Rizzo sounded like the GM of a team that had only minor maintenance left to do on his roster.

“I like our rotation. I like our bullpen,” Rizzo said. “I think we’re going to play better, smarter, more fundamental baseball [in 2012]. Davey [Johnson is] going to manage this team as good as any manager in baseball… We’d like to do some subtle things — improve our bench, improve our depth throughout the minor leagues.”

More on the Gio Gonzalez trade:

Thomas Boswell: Proof they’re ready to win now

Nats acquire Gio Gonzalez for four top prospects