Operating under the theory that you can never have enough pitching depth, the D-backs added a pair of right-handers Monday, acquiring Armando Galarraga from the Tigers for a pair of Minor Leaguers and signing Micah Owings to a Minor League contract.

"I'm really excited right now, I'm really happy and I'm looking forward to going over there to the National League and a new team," Galarraga said.

Galarraga would add depth to the back end of the D-backs rotation, which consists of Joe Saunders, Daniel Hudson, Ian Kennedy, Barry Enright and Zach Duke. The D-backs also agreed to give right-hander Aaron Heilman a chance to compete for a rotation spot when they re-signed him last week."I'd say he's got a fairly good shot of being in the rotation, but I want those guys to compete over the six weeks we're in Spring Training," D-backs GM Kevin Towers said. "We want to part with who we feel are our best five, and if Armando ends up being one of those five, he's going to be in our rotation."

Having to compete for a spot doesn't concern Galarraga.

"Everybody is going to fight for five spots," he said. "I believe in myself and I know I can do a lot of good things."

Minor League right-hander Kevin Eichhorn and left-hander Ryan Robowski head to Detroit with the D-backs picking up Galarraga's $2.3 million contract for 2011.

Should the D-backs not be impressed with Galarraga during the spring, they could release him by March 15 and owe him just 30 days' termination pay, or just under $380,000. If he's released by March 30, he'd be owed 45 days' pay, or just under $569,000.

On the other hand, if Galarraga pitches well, the team still has him under control for the next three seasons, which Towers considered a plus.

Galarraga became expendable and was designated for assignment last week when the Tigers signed free-agent pitcher Brad Penny. Towers and Tigers GM Dave Dombrowski initially had conversations about the deal Thursday, and Towers subsequently approached ownership about adding money to the payroll.

In addition to a fastball that sits in the 90-91 mph range and touches 93, Galarraga has a hard cutter/slider with his changeup being a distant third pitch.

"I think what would take him from a four or five starter to a two or three would be developing that third pitch," Towers said. "But I like the command, like the life on the fastball, the ability to pitch on both sides of the plate and the hard cutter. He's not a big strikeout pitcher; he does pitch to contact, but he works both sides of the plate really well."

Galarraga gained fame last season for his perfect game that wasn't when first-base umpire Jim Joyce incorrectly ruled Jason Donald safe at first base with two outs in the ninth inning. The right-hander went on to finish 2010 with a 4-9 record and a 4.49 ERA, becoming the first pitcher since Eric Hillman in 1993 to win four or fewer games despite having thrown at least 140 innings and posting an ERA below 4.50.

Galarraga led the Tigers in victories in 2008 when he was 13-7 with a 3.73 ERA, and he feels he can return to that form if he stays healthy and strong for a full season.

"In 2009 I was always hurt, my arm," Galarraga said. "2010, when I look back I don't see a bad year. Before September, I had a low 4 ERA."

Owings was originally drafted by the D-backs in the third round of the 2005 First-Year Player Draft and pitched in the big leagues for Arizona in 2007 and 2008 before being dealt to the Reds, with whom he went 10-14 with a 5.35 ERA over two seasons.

The D-backs will give Owings an invitation to Spring Training and allow him to compete for a long-relief role. Known for his hitting prowess at the plate, Towers said if Owings makes the team, he would add a power bat off the bench. Owings has nine homers in 198 career plate appearances.

"I would imagine he will see a little bit of time at first base -- how much time I couldn't tell you," Towers said. "We definitely want to get him some at-bats. He is kind of a dual-weapon guy and it would be nice to have a guy [where] on the days he may not be pitching, you still have a very good right-handed bat that could win a game for you."

Eichhorn was drafted by Arizona in the third round of the 2008 First-Year Player Draft and made 15 starts between Rookie ball and two Class A levels in 2010, going 5-6 with a 5.00 ERA. Robowski was 2-4 with a 5.17 ERA in 35 relief appearances for Class A Visalia last year.