"I never dreamed I'd be here by age 20," Penn said before Friday's game. "I was thinking Double-A by this time, but I am just going to enjoy this."
Penn is the latest Orioles prospect to get the call because of injuries and may be the most talented. He was 3-3 with a 3.12 ERA this year for Bowie, compiling a whopping 58 strikeouts in 49 innings. He quickly has emerged as the organization's top pitching prospect, surpassing Adam Loewen and John Maine.
Penn was the team's fifth-round pick in 2002 and a late signee, so he did not actually begin until roughly two years ago. He did not spend more than 13 outings with any Minor League team and advanced to Bowie in the final month of last season.
With a combined 9-9 record and 3.89 ERA in 2004, he was named the team's Minor League Pitcher of the Year. He then earned an invitation to Spring Training, where he made a positive impression on pitching coach Ray Miller.
"Just being around these guys, seeing how they handle themselves, gave me an idea what it's going to be like," he said. "That was a big help. Some of the guys told me I was going to get hazed, which is fine with me. The guys are doing their best to make me feel comfortable."
Penn said he got the word he was headed to Baltimore before Bowie's game on Thursday at New Hampshire, and then had the eight-hour bus ride from Manchester to think about his debut.
"Obviously, it will be tough to get some sleep, but I am going to treat it like it's any other start," he said. "The guys are telling me that it's still baseball, it's still a game, so go out and have fun."
Orioles manager Lee Mazzilli became familiar with Penn in Spring Training and is anxious to see the youngster pitch.
"We want to see what he's got," Mazzilli said. "We think this will be good for him. We'll give him a couple of starts and see what happens. But we like the kid's makeup. He wouldn't be here if we didn't think he could succeed."
Penn will be the eighth-youngest pitcher to debut in Orioles history and the first age 20 or younger since Matt Riley in 1999. The younger Orioles pitcher to make his debut was the late Dave McNally, who was 19 when he toed the rubber in 1962.
Gibbons gets break: Against Detroit left-hander Nate Robertson, right fielder Jay Gibbons got his first day off since April 30. Gibbons is hitting .333 (13-for-39) in his past 11 games and a respectable .243 against left-handers.
Sammy Sosa started in right field and Chris Gomez was the designated hitter.
Farm report: Maine, who was a candidate to be promoted for Saturday's start, allowed just two runs in seven innings but was the hard-luck loser in a 4-1 Ottawa loss to Norfolk. Maine (3-3, 3.65 ERA) struck out four and walked one.
Eli Whiteside knocked in the Lynx's lone run.
Coming up: The Orioles face the Tigers in the second of a three-game series at Camden Yards on Saturday. Penn takes on former Oriole Jason Johnson (2-4, 3.55 ERA). Johnson allowed two runs in seven innings against the Orioles to improve his overall record against them to 1-1.