"He's got that pronator strain that's still going on," manager Bruce Bochy said of Melancon. "He threw great last time -- good stuff. But it showed up and he could really feel it. We need to get this behind us."
Bochy said he wasn't sure exactly how long Melancon will be unavailable. The 32-year-old received a platelet rich plasma (PRP) shot Wednesday and had an MRI Tuesday morning, which showed inflammation.
"After the DL, there was a week or so where it was good, then it kind of came back," Melancon said. "Maybe I rushed coming off the DL a little too early. Being the first time on the DL, it felt really awkward. … Probably wasn't the smartest decision to rush out."
Bochy said he wasn't sure exactly how long Melancon will be unavailable, but Melancon will undergo an MRI on Wednesday.
The Giants' prized offseason acquisition has allowed seven earned runs in 10 innings since returning to the mound on May 19. He hadn't allowed a run in his past three outings.
"We need to get over the hump," said Melancon, who will fly with the team to Pittsburgh. "Felt like some rest and PRP is the only way to do that."
Slania would be the latest in a parade of Giants prospects to make his Major League debut. He owns a 1-9 record with a 6.44 ERA in 15 starts between Richmond and Sacramento this season. Bochy said Slania is flying to San Francisco from Trenton, N.J., but he has experienced a flight delay.
"He's a guy that can help give us some insurance here with a fresh arm in the bullpen," Bochy said. "He had a great year last year. It's been an up-and-down year this year, but the key thing right now is that he's the freshest arm we have."
Bochy said right-hander Sam Dyson will assume closing duties with Melancon sidelined. In his career, Dyson has compiled 40 saves, including 38 with the Rangers in 2016. Hunter Strickland earned the save Wednesday as the Giants defeated the Rockies, 5-3, to secure a sweep.
"It's another pretty good blow we just took," Bochy said of Melancon's symptoms. "We got to overcome that. But it's all about keeping the right attitude and fighting."
Fantasy spin | Fred Zinkie (@FredZinkieMLB) Fantasy owners are no doubt disappointed by Melancon, who has produced 11 saves with a 4.35 ERA after entering the season ranked in the top tier of closers. But with 147 saves and a 1.80 ERA from 2013-16, the righty should be retained on the hope that he will return from injury to participate in a significant portion of San Francisco's remaining games. Deep-league Melancon owners should scan waivers for Dyson, while those in shallow leagues can consider Santiago Casilla, Brandon Maurer or Hector Neris.
Jonathan Hawthorne is a reporter for MLB.com based in the Bay Area.