(Sports Network) - The Arizona Diamondbacks will unveil their prized offseason acquisition in tonight's middle matchup of the club's season-opening three- game set with the host Cincinnati Reds, as Dan Haren makes his first start as a member of the defending National League West champions.

In one of the most aggressive moves of this past winter, Arizona general manager Josh Byrnes shipped six young players -- including three well-regarded prospects -- to the Oakland Athletics to reel in Haren, the American League's starting pitcher in the 2007 All-Star Game. The addition of the hard-throwing right-hander to a rotation that includes 2006 NL Cy Young Award winner Brandon Webb and at some point will have future Hall of Famer Randy Johnson has made the Diamondbacks one of the preseason favorites to represent the Senior Circuit in this years World Series.

Haren won 14 or more games in each of his three seasons with the A's and finished third among AL hurlers with a 3.09 earned run average last year. The Pepperdine product also struck out a career-best 192 batters and compiled a 15-9 record in 34 starts.

The 27-year-old has faced Cincinnati three times previously, two of them starts, and went 1-1 with a 5.93 ERA in those outings. Haren did beat the Reds with seven innings of three-run ball in Oakland last June.

Webb's 2008 debut went pretty smoothly for Arizona, as the sinker specialist held the Reds to two runs over six innings to help the Diamondbacks to a 4-2 victory in Monday's opener.

Webb yielded just three hits and struck out six before turning things over to the Arizona bullpen, which got scoreless frames out of Chad Qualls and Tony Pena before Brandon Lyon picked up the save with a 1-2-3 ninth.

The Diamondbacks gave Webb enough support with the long ball, as Chris Young, Eric Byrnes and Jeff Salazar all hit solo home runs on the afternoon.

Aaron Harang was saddled with the loss after allowing three runs -- two earned -- in six innings of work. The Cincinnati ace also gave up just three hits and struck out six.

The Reds will try to even things up tonight behind Bronson Arroyo, who seeks a return to his 2006 form after a disappointing last season.

Arroyo went 14-11 and placed fourth in the NL with a 3.29 ERA in his first season in Cincinnati, but slipped to 9-15 with a 4.23 ERA in 2007. Home runs led to his downfall a year ago, as Arroyo served up 28 of them in 210-plus innings of work.

The free-spirited right-hander has never beaten Arizona in five lifetime tries (three starts), having produced an 0-2 record with a 4.56 ERA in 25 2/3 innings.

The Reds swept a three-game series from Arizona in Cincinnati last July and won four of the six overall encounters between these teams in 2007. The Diamondbacks had gone 3-6 over their nine most recent games at Great American Ball Park prior to Monday's triumph.