BALTIMORE -- The Orioles lost a key arm for the season on Wednesday, when they learned Alfredo Simon will need reconstructive surgery on his pitching elbow. Simon, who originally was feared out for a month or more, likely will spend an entire year on the sideline to rest and rehabilitate his injured joint.

Simon injured his elbow in his second start of the season, and Baltimore's front office said the initial symptom of the ailment was a distressing drop in velocity. Simon has since been replaced in the rotation by rookie Brad Bergesen, and the Orioles still are waiting for Rich Hill to return from the disabled list.

Andy MacPhail, Baltimore's president of baseball operations, said Simon's injury illustrates how difficult it is to build a stable pitching staff and keep it rolling through an entire regular season.

"That's why you start with 36 [pitchers]. It's not unique to us," MacPhail said. "Pitching is a really fragile commodity, and it's an erratic commodity. That's why you have to have as many numbers as you can and allow for the inevitable things that are going to evolve over the course of a six-month, 162-game season."

Simon, who was signed out of the Mexican League late last season, expects to have his operation conducted by noted surgeon James Andrews. The right-hander, who earned his rotation slot with a strong Spring Training, was disappointed to lose his chance to establish himself so early in the season.

"They gave me the opportunity, and I can do the job," said Simon, who is 0-1 with a 7.45 ERA for his career. "But my elbow doesn't have ligaments. So I am going to do the best I can to come back next year."

The 27-year-old went five innings against the Yankees in his season debut, but he was a different pitcher when he met the Rangers on April 14. Simon's velocity was in the mid-80s against Texas, and he gave up three home runs in the first two innings. O's manager Dave Trembley lifted him after the third home run, fearing an injury.

"You could see right away. He went from 94 [mph] to 86-to-90," said MacPhail of Simon's velocity. "To be honest with you, it's tough for us, but I'm more disappointed for the kid. You think about what the kid had at stake. He had an opportunity here. He pitched well in the spring, but as is the nature of this game, it can evaporate in a hurry. Hopefully things will come back, and in a year or so, he can get back to where he was."

Part of Simon's anxiety regarding the surgery might be lessened by the knowledge that two of his teammates -- Danys Baez and Chris Ray -- recently have come back from a similar procedure. Both Baez and Ray missed all of last season, but they have returned this year pain-free and back to their old velocity.

"They talked to me about this," said Simon, speaking about Baez and Ray. "I have to work hard, and I know it. It's better to do the decision now. And for next year, I think I am going to be ready."