MIAMI -- The Nationals called up veteran relievers Fernando Rodney and Jonny Venters in hopes of bolstering their beleaguered bullpen prior to Tuesday's 6-1 win over the Marlins at Marlins Park. Rodney made his Washington debut with a scoreless ninth inning.

Nationals manager Dave Martinez said the pair "checked all the boxes" in regard to the timing of its return to the Majors. Both Rodney and Venters had upped their pitch counts, worked back-to-back games, thrown strikes and shown high velocity.

"Beyond their numbers, they're throwing the ball really well," said Martinez, who knows Rodney from their days with the Rays and Cubs. "In order for both of those guys to be successful, they've got to keep the ball down. Look forward to watching them pitch. I've known Fernando for a long, long time now. When he's on, he's really good. I talked to him today, said he feels good and he's ready to help us in any way."

Rodney, who has 325 career saves, began the season with the A's before being designated for assignment after compiling a 9.42 ERA and 2.23 WHIP in 17 appearances. Upon signing with Washington earlier this month, Rodney gave up five runs (four earned) over eight innings spanning nine outings at Triple-A Fresno.

The 42-year-old right-hander is the oldest active pitcher in the Majors. He experienced success as recently as last season -- his 16th in the big leagues -- by posting a combined 3.36 ERA and 127 ERA+ between the Twins and A's over 68 games. Rodney made Oakland's American League Wild Card Game roster.

"I didn't feel comfortable in that situation that happened earlier in the season, so I go to the office and tell skip, 'I'm not going to help you like that pitching every five, four days, let me go to some team and contribute and help a team to win,'" Rodney said. "They let me go, and the Nationals picked me up."

Venters signed a Minor League deal with the Nationals on May 29, less than two weeks after being released by the Braves. He allowed 13 runs (nine earned) over 4 2/3 frames with Atlanta, and he also missed time with a calf strain.

At Double-A Harrisburg, Venters scattered six hits and permitted one run with four strikeouts and six walks over seven innings.

The 34-year-old southpaw pitched in the Majors last season for the first time since 2012 after undergoing the second and third Tommy John surgeries of his career. He won the National League Comeback Player of the Year Award with a 3.67 ERA and 115 ERA+ over 50 appearances.

"Beginning of the season was tough. I didn't pitch well, I didn't throw a lot of strikes and when I did, it seemed to get hit pretty hard," Venters said. "Between then and now, I've really just grinded, made some adjustments on my delivery and how I was pitching guys. Just try and throw in the zone, throw some strikes and get some swings early. So, hopefully that will carry over."

Postseason hopeful Washington, which won 18 of its previous 27 games entering Tuesday and sat eight back of the NL East-leading Braves, continues to search for relief help. The Nats entered Tuesday with the NL's highest bullpen ERA (6.29). On Sunday, the club released righty Trevor Rosenthal, who recorded a 22.74 ERA over 12 appearances after signing a one-year, $7 million contract over the offseason.

"You're going to have to be ready to pitch any given day," Martinez said of what Rodney's and Venters' roles would be. "They'll have some high-leverage situations. I like Venters, especially against lefties. And Rodney, he was a closer for many, many years, so he understands high-leverage situations. We'll see how they fit in."

Nats targeting weekend return for Zimmerman

First baseman Ryan Zimmerman, on the injured list since April 28 with plantar fasciitis in his right foot, went 0-for-4 as the designated hitter for Harrisburg on Tuesday. Barring any setbacks, he will join the Nationals for their weekend series in Detroit against the Tigers.

"If everything goes well from now until then, he'll meet us in Detroit," Martinez said. "He had a good day [Monday], he'll DH [Tuesday] and hopefully, if he feels good, play nine innings [Wednesday] and we'll see where we're at."

Zimmerman batted .213/.302/.373 with three doubles, three homers and 11 RBIs over 22 games prior to the injury. Entering Tuesday, he had gone 3-for-8 with a walk and an RBI in three rehab games.

Voth over Fedde in rotation ... for now

Right-hander Austin Voth, who allowed two runs over six innings in Sunday's 4-3 loss to the Braves, has earned another start this weekend in Detroit. The Nats optioned righty Erick Fedde to Triple-A Fresno following Sunday’s series finale. He was chased in the fourth inning of last Thursday's start against the Phillies after allowing two runs on five hits and five walks.

"After seeing what Voth did his previous outing here, we thought, 'Why not give him another chance?'" Martinez said. "He's getting a start in Detroit, and we'll see where we're at from there."

Worth noting

In Tuesday's corresponding roster moves, the Nationals optioned right-hander Kyle McGowin to Triple-A and transferred righty Jeremy Hellickson (stiff right shoulder) to the 60-day injured list.