Ian Kennedy, Wade Miley, Trevor Cahill and free agent signee Brandon McCarthy will likely fill the first four spots in the rotation for manager Kirk Gibson this season. After that, it gets interesting.

"I think we've got two young kids and (Randall) Delgado right now," Gibson said Monday as his pitchers and catchers reported to Salt River Fields at Talking Stick. "Right now, it's (Tyler) Skaggs, (Patrick) Corbin and Delgado -- there's some others in there too, but it's definitely a competition spot."

Skaggs is probably the most intriguing of the candidates. The 21-year-old lefty got his first taste of "the show" last season, starting six games for Arizona and posting a 1-3 record with a 5.83 ERA. But Skaggs pitched well in the minor leagues in 2012, going 9-6 with a 2.87 ERA in 22 starts between Double-A Mobile and Triple-A Reno.

He's also rated as the Diamondbacks' top prospect by Baseball America and ESPN's Keith Law sees Skaggs as the 12th-best prospect in all of baseball (and tops among left-handed pitchers).

Corbin is another highly-touted lefty who showed versatility while pitching in 22 games with Arizona last season. Corbin went 6-8 with a 4.54 ERA in 17 starts and five relief appearances for the Diamondbacks, but also notched a 5-2 record and a 2.84 ERA in 13 minor league starts with Mobile and Reno.

Delgado, who came to Arizona in the deal that sent Justin Upton to Atlanta, is also young -- only 23 years of age. In 2012, the right-hander went 4-9 with a 4.37 ERA in 17 starts with the Braves. Heading into the 2012 campaign, Delgado was rated as Atlanta's third-best prospect by Baseball America.

Gibson did mention "others" being in the mix, and that could very well mean 27-year-old right-hander Josh Collmenter, who has made 35 starts over the last two seasons, could be vying for the fifth spot as well. But Collmenter has shown to be very effective out of the bullpen, posting a career 1.31 ERA and a very good 1.042 WHIP in 24 relief appearances.