The bullpen also has multi-inning options in right-hander Edwin Jackson and lefties Chris Narveson and Craig Breslow.
Barraclough saw action in his first game back in the Majors during the Marlins' 6-5 loss to the Braves on Sunday. The right-hander threw a scoreless seventh inning, striking out three while walking one and allowing one hit.
The question with Barraclough is whether he will throw enough strikes to become a true factor in the bullpen. If he does, his impact could be huge as the team tries to recover from a slow start.
"We'll see with Kyle," Mattingly said. "Kyle is a guy who misses bats. He's got a wipeout slider. He's got power stuff. He's kind of what we've been missing a little bit."
Entering Spring Training, Barraclough was a frontrunner to make the Opening Day roster, especially after Carter Capps underwent Tommy John surgery. But he was wild, walking eight while striking out eight in 6 1/3 Grapefruit League innings.
"We kind of had designs on him at some point," Mattingly said. "We didn't know how long it would take -- whether it was going to be a month, two months, two weeks. We weren't sure when it was going to be."
Ranked No. 20 among Marlins prospects by MLBPipeline.com, Barraclough got off to a hot start at New Orleans, striking out nine while walking one in six innings. The 25-year-old was used in multiple-inning situations at Triple-A, and he offers that flexibility with the Marlins, but Mattingly is leaning toward limiting him to one inning per outing.
"He went down," Mattingly said. "He's throwing strikes. He's been effective. He's proven that he can pitch here last year. Just in spring, it seemed rough. It seemed everything was going fast for him in the spring."
Barraclough's fastball last year averaged 95.6 mph. Acquired from the Cardinals for Steve Cishek, he appeared in 25 games and had a 2.59 ERA, striking out 30 in 24 1/3 innings for the Marlins in 2015.
"He was a guy in Spring Training, before Carter got hurt, who was a true option in that bullpen," Mattingly said. "It seemed like he was all over the place in spring. I don't know if he was putting too much pressure on himself in the spring."
Mattingly added he is trying to maximize Phelps' effectiveness by limiting him to one inning.
Although Phelps has been a starter and long reliever, he is locking himself into the eighth-inning spot with his early success and likely would get chances to close out games if Ramos isn't available.
"We want to use Phelps later and want to try to keep him at one [inning]," Mattingly said. "And not have to think about him at two. Trying to keep him strong."