The fourth-winningest pitcher in D-backs history, Ian Kennedy is slated to start his third consecutive Opening Day for Arizona. After a stellar 21-win 2011 campaign with a 2.88 ERA, Kennedy struggled to match that performance again in 2012, accruing 15 victories and a 4.02 ERA.

Trevor Cahill will fill the slot behind Kennedy. In his first season as a D-back, the fourth-year pitcher won 13 games in 32 starts while carrying a 3.78 ERA.

Southpaw Wade Miley, 16-game winner and last year's runner-up for the NL Rookie of the Year Award, will be the third starter.

Brandon McCarthy is expected to fill the club's fourth spot in the rotation. On Tuesday McCarthy pitched in his first game back since suffering a head injury last season, surrendering one run in two innings against the Cincinnati Reds.

Behind McCarthy, three pitchers -- Tyler Skaggs, Patrick Corbin and Randall Delgado -- are unofficially vying for the fifth and final spot.

One week into spring training each has made a start, and top pitching prospect Skaggs made his second appearance in relief Thursday.

That may leave a small sample size of play to be analyzed, however, pitchers are only allotted so many starts throughout the month, which makes every inning count that much more.

Skaggs had a shaky first start Saturday versus the Colorado Rockies. In 1.2 innings, he struck out two and allowed four runs -- two earned, two unearned - on four hits.

Things went from bad to worse Thursday in Goodyear against the Reds when he pitched two-thirds of an inning. Skaggs balked and threw a wild pitch on top of allowing three runs and two walks. He also had a strikeout.

"Pitched terrible. That's it," he said after the outing.

In two solid innings Sunday against the Rockies, Corbin yielded a hit and a walk while striking out four.

Delgado was lit up against the Kansas City Royals Monday, giving up six hits and five runs -- four earned -- in an inning pitched.

With the entire month of March left for the trio to show what they've got, plenty can change, though it's easy to see Gibson won't have an easy decision on his hands.