Nats acquire closer Melancon for Rivero, Hearn (updated)

SAN FRANCISCO - The Nationals have found their much-needed closer, and though he's only going to be a two-month rental, the club didn't have to give up any of its top prospects to get him.

The Nationals have acquired Mark Melancon from the Pirates in exchange for left-hander Felipe Rivero and Single-A left-hander Taylor Hearn, the team announced this afternoon.

The deal came together just before the scheduled 4:05 p.m. EDT first pitch of today's game against the Giants, allowing the Nationals to clear a roster spot necessary to make room for starter Reynaldo Lopez.

Melancon is expected to join the team in San Francisco on Sunday.

"Obviously they're doing great, and full with talent," the reliever told reporters in Milwaukee, where the Pirates are playing this weekend. "It's crazy, because you have to play both sides. I'm still in the Pirates clubhouse, and it's like, man, it's tough. And then you step outside, and now there's excitement, too. Obviously, I'm excited to go there and be a part of something that looks very opportunistic."

Melancon may not draw the attention afforded to elite major league closers like Aroldis Chapman and Wade Davis, but he has been just as consistently dominant over a significant period of time: The right-hander owns a 1.80 ERA and 0.926 WHIP over the last four seasons.

Melancon, who has a 1.51 ERA and 30 saves in 33 opportunities this season, will be eligible for free agency this fall. It remains to be seen whether the Nationals will attempt to re-sign the 32-year-old, but for now short-term needs outweighed long-term security.

With Jonathan Papelbon mired in a major funk over the last week and facing an uncertain future, the Nationals felt they had no choice but to acquire a proven closer before Monday's trade deadline. It's unclear what Papelbon's role will be now, but manager Dusty Baker said this morning the 35-year-old continues to insist he's not injured despite decreased velocity.

General manager Mike Rizzo had been adamant throughout trade talks that he would not include any of his top four prospects (Lucas Giolito, Trea Turner, Lopez, Victor Robles) in any deal. That prevented him from swinging a trade for Chapman, who wound up going to the Cubs for a package of elite prospects.

But Rizzo still managed to acquire one of the game's best closers without giving up any of those four.

Which isn't to say Rivero is chump change. The 25-year-old left-hander has an electric arm that approaches triple digits, and he has five more years of club control after this season. But the Nationals' immediate need for someone who can pitch the ninth inning, along with the emergence of fellow lefty Sammy Solis, helped make the loss of Rivero more tolerable for the club.

Hearn, meanwhile, was a fifth-round pick in the 2015 draft. The left-hander has a 2.79 ERA in 10 games (four starts) between low Single-A Hagerstown and the rookie Gulf Coast League in his first professional season.

MASNsports.com's Byron Kerr contributed to this report.