Pearce, who was surrounded by teammates following the news and is very well-liked in the clubhouse, saw very limited playing time this season. He made just one start and was 1-for-7 with appearances in three games total.
McFarland, who was scheduled to start for Triple-A Norfolk on Tuesday, gives the Orioles another multi-inning option to go with Josh Stinson, as the O's are coming off a series in which their starters covered just 21 2/3 innings in four games. The lefty was the Orioles' Rule 5 Draft pick last season and competed for a starting spot this spring.
"It was just one of those things. Buck likes me. He didn't want to make the move, but ultimately it was best for the team," Pearce said. "It was the only logical move they could make. I was just the odd man out.
"It's difficult. I'm going to miss the guys. It's tough. Having to leave the team, getting designated for assignment, nobody likes it, but it comes with the territory. It's part of the game. I understand that. I have no bad blood toward anybody. It's just the way it works."
Pearce will likely be claimed by another team, but if he's not, he could opt to return to the Orioles organization in Triple-A.
"The only way I make it work for me is knowing it's best for Steve, and he's going to come out OK one way or the other," Showalter said. "Staying with us [if he clears waivers] is OK, too. I like him."
Brittany Ghiroli is a reporter for MLB.com. Read her blog, Britt's Bird Watch, and follow her on Facebook and Twitter @britt_ghiroli. This story was not subject to the approval of Major League Baseball or its clubs.