Elbow injury threatens Patrick Corbin's season, Arizona's rotation depth

Patrick Corbin's season is in jeopardy due to a partially torn elbow ligament. (Gregory Bull/AP) The Diamondbacks open their season ahead of the rest of the

Patrick Corbin's season is in jeopardy due to a partially torn elbow ligament. (Gregory Bull/AP)

The Diamondbacks open their season ahead of the rest of the major leagues thanks to a series in Australia against the Dodgers, but already it appears that Arizona has suffered a major loss. On Sunday, the team revealed that scheduled Opening Day starter Patrick Corbin has a partially torn ulnar collateral ligament. The 24-year-old lefty may face Tommy John surgery, and even if he doesn't, he'll miss significant time for an injury that will test the depth of the Diamondbacks' rotation.

On Saturday, Corbin left his final Cactus League tuneup in the middle of a seventh inning at-bat due to stiffness in his left forearm, and a subsequent MRI by team doctors revealed damage to his UCL. Instead of heading to Australia, he will visit Dr. James Andrews for a second opinion as to whether surgery or rehabilitation is the best course of action. The former would cost him at least the entire 2014 season, while the latter would still keep him sidelined for months, perhaps only forestalling the inevitable.

Either way, Corbin's injury is a significant blow to the Diamondbacks, as he was their most effective pitcher last year. In his first full major league season, he earned All-Star honors, posting a 3.41 ERA (112 ERA+) over 208 1/3 innings with a strong 3.3 strikeout-to-walk ratio. As good as that showing was, his late-season fade generated some amount of concern. In 25 starts through August 20, he put up a stellar 2.45 ERA while striking out 21.8 percent of hitters, but over his final seven starts, he was torched for an 8.00 ERA in whiffing just 16.3 percent. His home-run rate nearly tripled across that split, from 0.63 per nine to 1.75, and where 20 of his first 25 starts were quality starts, just two of his final seven were. He lasted just 11 1/3 innings over his final three starts, allowing 23 hits and 15 runs.

It's possible that Corbin may have already been pitching through some amount of damage. Though he had performed effectively in his first three spring starts, Corbin revealed at his press conference Sunday that he had been experiencing tightness in his forearm through much of spring training. As he finished off his 91-pitch outing on Saturday, the pain rose to a new level; via the Arizona Republic's Nick Piecoro, here's what Corbin had to say:

"It just kind of felt like a small little shock in there," he said. "Nothing popped or anything like that. It was just a different feel that I wasn't used to and just really uncomfortable."

It's fair to ask whether Corbin's woes were exacerbated by the pending trip to Australia, which moved Opening Day for the Diamondbacks and Dodgers to March 22. The NL West rivals will play two games down under before returning stateside for more exhibitions, with the next regular season opener not until Sunday, March 30, and the first full slate of games — Opening Day for 26 teams — not until Monday, March 31. The two Australia-bound teams opened camp about a week ahead of everybody else, but that's still a compressed schedule relative to the end of the 2013 season, and the season-opening assignment may have created additional pressure on Corbin to ramp up his pitch count in order to justify the start.

With Corbin sidelined, the Diamondbacks will reshuffle their rotation. Fellow lefty Wade Miley, their second-most effective pitcher in 2013 in terms of both ERA (3.55) and workload (202 2/3 innings) will take the ball for the opener. Trevor Cahill and Brandon McCarthy will start the season in the rotation, with the former slated to face the Dodgers on March 23. Meanwhile, the team hopes Bronson Arroyo will be ready for the opening bell. The 37-year-old is behind schedule due to a bulging disk in his back, a recurring problem for which he received treatment earlier this month. He did throw a 50-pitch bullpen session on Sunday and is scheduled to throw a simulated game on March 19, followed by a minor league exhibition start on March 24. That would allow the team to backdate a disabled list stint, something Arroyo — who has made at least 32 starts while averaging 211 innings a year over the past nine seasons — hasn't experienced in his major league career.

CORCORAN: Josh Beckett, Michael Pineda among pitchers working way back from injury

The Diamondbacks don't resume regular season play until March 31, but with a stretch of seven games in seven days, they'll need a fifth starter on April 4, and that's where the intrigue ramps up. Randall Delgado, who made 19 starts and one relief appearance for Arizona in 2013, and Josh Collmenter, who spent last year in the bullpen after making 35 starts in 2011-12, are tried-and-true options who were slated to start the year in the big club's bullpen. The former pitched to a 4.26 ERA in 116 1/3 innings for the Diamondbacks last year but allowed more homers (1.9 per nine) than walks (1.8 per nine), and the latter put up a 3.13 ERA out of the bullpen.

The real question is whether 21-year-old righty Archie Bradley, considered by many to be the top pitching prospect in the minors, could start the year in the majors, a possibility that seemed remote when the team signed Arroyo back in February. The No. 7 pick of the 2011 draft dominated at High-A and Double-A in 2013, so much so that he was promoted after just five starts at the first stop; he finished the year with a 1.84 ERA and 9.6 strikeouts per nine in 152 innings. Despite outstanding stuff — a 92-98 mph heavy fastball and power curve that are both considered near-elite pitches — he has command issues borne from an inconsistent delivery that he needs to iron out. Bradley walked 4.3 per nine at Double-A Mobile, and struggled to find the plate in his March 13 start against the Mariners, walking the leadoff hitter in each of his two innings and needing 61 pitches to get through through an outing that manager Kirk Gibson called "kind of a stinker."

VERDUCCI: Is Diamondbacks' Bradley the next pitching phenom?

Beyond the in-house options, the Diamondbacks are expected to revisit discussions with the Cubs over Jeff Samardzija, who has struck out more than a batter per inning in each of the past two seasons but saw his ERA inflate to 4.34 last year. The Cubs spent the winter fielding offers on Samardzija while trying to work out a long-term extension with the 29-year-old righty, who can become a free agent after the 2015 season. The Blue Jays, Braves and Diamondbacks were said to be the three most interested teams, but with the signing of Arroyo, Arizona's interest appeared to have cooled.

Kris Medlen

Brandon Beachy

Oakland's Jarrod Parker

scheduled to visit Dr. Andrews

Cory Luebke

Luke Hochevar

is scheduled to undergo the surgery