LeBlanc -- whose start Monday was his first Major League one in 15 months, and his shortest in three years -- was shelled for six runs on seven hits and three walks, providing only a brief respite for a tired bullpen. He was designated for assignment by the Angels for the second time this season.
The Angels added reliever Yoslan Herrera for bullpen depth.
"I think we have confidence is what Wade can do when he's throwing the ball to his capabilities," Angels manager Mike Scioscia said. "Last night, we didn't see that.
"This isn't a reactionary move to a bad outing from last night to say that we're looking past Wade LeBlanc. Right now, in the short term, we have to because we really don't have many options for these next couple days, and you need a fresh arm out there."
LeBlanc started in place of injured right-hander Garrett Richards, who was lost for the season when he tore his patellar tendon in Boston on Wednesday. Richards was having a breakout season (13-4, 2.61 ERA), and his injury only depleted an already thin pitching staff that was without Tyler Skaggs.
With LeBlanc crossed off the list -- and Saturday's start against Oakland left vacant -- the Angels must now scramble to fill a rotation spot.
Possible options include Triple-A arms Randy Wolf (0-1, 4.99 ERA) and Chris Volstad (2-1, 6.18), or Double-A starters Michael Roth (11-7, 2.62) and Drew Rucinski (10-6, 3.22).
Roth and Rucinski are currently on the 40-man roster, meaning the Angels could recall either one without having to lose anyone from their roster. Roth is perhaps the most likely to start after throwing seven shutout innings for Arkansas on Monday night.
The Angels could also pick up a pitcher via waivers to shore up the back end of the rotation. Mets starter Bartolo Colon and Astros starter Scott Feldman both reportedly cleared waivers on Monday.
"If you're asking me, 'Does our team need pitching depth?' my answer is going to be the same even if we have a full contingent of Garrett Richards here and Tyler Skaggs," Scioscia said. "You'd say, 'Yes, you need pitching depth.' That's just the nature of this game. You always need to pay attention to your pitching depth, and I know that we are."