The 27-year-old Melancon faced six batters on Tuesday night and did not retire any, giving up three homers and walking two in Boston's 18-3 loss to the Texas Rangers.
He became the eighth pitcher in the past 90 years to allow three home runs without recording an out, and the first Red Sox reliever to allow a homer in three straight appearances since Terry Adams in 2004, according to ESPN Stats & Information. The disastrous outing raised his ERA on the season to a staggering 49.50.
The Red Sox called up right-hander Junichi Tazawa to take his place.
Red Sox manager Bobby Valentine said Melancon was receptive to the demotion.
"He walked into the office and he said, 'When do I leave? How soon can I get on the mound again?' He realized it wasn't going to be here," Valentine said in an interview on Boston sports radio station WEEI. "He realized he needed some regular work. In the opportunities he's had here, he hasn't really had any kind of flow to it. It's waiting around seeing when the opportunity will arise and you know his command has just been something other than he wants it to be. He's ready to go to work, though. He's really a pro."
Melancon, acquired in the offseason in a trade from the Houston Astros for shortstop Jed Lowrie and pitcher Kyle Weiland, has given up five homers and 11 runs over a combined two innings. He has appeared in four games for Boston and has given up at least a run in each game.
After closer Andrew Bailey went down late in spring training with a thumb injury, Valentine said Melancon would be part of the mix to help close games in Bailey's absence. That, obviously, has not worked out.
Melancon took the loss on Opening Day in Detroit, thanks to Alfredo Aceves' blown save, and then blew a save of his own in the third and final game of the series on an 11th-inning walkoff homer by Alex Avila.
Melancon gave up a homer to Tampa Bay's Ben Zobrist in completing one mop-up inning last Friday, and then there was this meltdown against the Rangers in which he surrendered homers to Josh Hamilton, Adrian Beltre and Nelson Cruz.
"I have to believe it's going to get better," Melancon said in the Sox clubhouse after Tuesday's game. "Mentally, I feel good. Physically, I feel good. It's close. I'll figure it out. I've only had four outings, but it's gotten out of hand pretty quickly."
Valentine said Melancon's issues are not injury related.
"We asked. He said absolutely not," said Valentine on Wednesday in his daily briefing with the media.
"He just has to be the pitcher he is. He struggled with his command. He's a 'command' pitcher, and we didn't feel he'd have the opportunity here to work through it," Valentine said.
Last season as the Astros closer, Melancon was 8-4 with a 2.78 ERA and 20 saves in 71 games. He allowed five homers in 74 1/3 innings.
Information from Steven Kranser was used in this report.