"He never seemed to get in a real rhythm," Showalter said. "Philadephia had a lot to do with that. They came out swinging the bats real aggressive, like we knew they would and have been all year. It's kind of tough to figure because he was in stride a little bit there and strikes out three or four and looks like he's going to be able to give us four or five and it just didn't materialize.
"It's not good. Jake knows that. It's not good enough."
Arrieta struck out the side in the third after the Phillies sent 10 batters to the plate in the second. He served up a two-run homer to Shane Victorino in the fourth.
"It probably tells you there are probably some other things going on besides physical issues," Showalter said. "It's a challenging game. I'm sure it's frustrating for Jake because he's in great shape, his arm feels good. There are a lot of things in his corner, but he just can't get it to happen on the field."
Asked if starts like this are chipping away at Arrieta's confidence, Showalter said, "Obviously, yeah. That's human nature. There's an ebb and flow to all states of where you are mentally. That's part of it. But it's also part of making that step into being a consistent guy who your team can count on every fifth day. It's hard to do. That's why guys who can do that are in such high demand."
Showalter confirmed that Tommy Hunter will start tomorrow, but he didn't speculate whether Arrieta could be optioned.
"I understand how things float around," he said. "You have a tough start like that, there's a lot of emotion going around. I'm sure by Jake, too. The last thing anybody needs is me weighing in on it publicly. I know you've got to ask it. We'll sit down and see what the best move for us is.
"We know Jake is capable of a lot better, but I think everybody knows we expect some of our young pitchers with their experiences that they've had to graduate to a little bit more consistency."
Brian Matusz lasted two innings and one batter in the third last night in Boston. Showalter was trying to avoid pulling another starter in the early innings. He also wanted to give Arrieta the chance to steady himself.
"We were trying to let him get in step and give us some innings," Showalter said. "You have two early knockouts like that in a row, it can really put a real stress on your bullpen. We don't have another off day for a while, so you're trying to get through that the best you can. As fast as it happened, I'm not going to bring Dana (Eveland) in until he's physically ready, too."
The Orioles kept trying to fight back, and J.J. Hardy's two-run homer in the seventh brought them within three.
"That's a given with this group of guys," Showalter said. "Just a little frustrating because there are certain holes you feel like you can dig out of. Heck, we were close to getting the tying run to the plate there in the eighth. I'm proud of that part. You can certainly take some good things out of it if you try to.
"We didn't exactly help him a little bit. There were probably a couple plays we should have made that could have shortened that. There's two or three outs we kind of gave them, the pop up and some other things we should have done better."