Sarah's Take: D-backs in jam without Miller

The Diamondbacks and the Rockies are the surprise teams in the National League West. Both are playing well above pundits' expectations.
These teams will go as far as their pitching will carry them, and the D-backs received some devastating news during the weekend when they learned Shelby Miller will need Tommy John elbow surgery.
The D-backs traded for Miller from the Atlanta Braves in December 2015. Though he had a losing record (6-17) in 2015 due to a lack of run support, Miller was an All-Star that year. The D-backs gave two of their top Minor League prospects to the Braves to acquire Miller, but the deal made sense for the D-backs, who needed to rebuild their starting rotation.
Miller had a disastrous 2016 season, going 3-12 with a 6.15 ERA. Mechanical problems affected his performance adversely, even caused him to scrape his right knuckles on the mound while delivering a pitch. The D-backs couldn't straighten out his mechanical problems even when they demoted Miller to Triple-A.
This past offseason Miller worked hard, and when he reported to Spring Training he was in the best shape of his life. With new mechanics, he earned a spot in the starting rotation. In his four starts this season, Miller was 2-2 with a 4.09 ERA. Last Sunday he was sailing along against the Dodgers until the fifth inning when he suddenly lost control. Though he was charged with the loss, it was obvious something was wrong with Miller.
The initial report was a tight right forearm, which is never good news for a pitcher. On Thursday, it was revealed Miller has a torn UCL. After weighing his options, Miller decided on Friday he will undergo Tommy John surgery.
So far, the D-backs have the second-best starting rotation in the National League with a 3.34 ERA. Robbie Ray looks like he has matured as a pitcher. Zack Greinke continues to learn how to dominate with diminished velocity. The rest of the rotation has improved from last year.
Knowledgeable baseball people have concerns about the D-backs' bullpen. So far, it hasn't been good with a 4.72 ERA.
Undoubtedly, the D-backs have a great offense, averaging 5.2 runs per game. They will have a much better offense than last year when injuries snake bit the team. A.J. Pollock is back from a broken elbow, and he will help to improve the offense and defense. Yasmany Tomás has learned the league, and understands the strike zone better. Jake Lamb continues to mature as a hitter. Paul Goldschmidt is a perennial MVP candidate.
It will be interesting to see how the D-backs respond to Miller's injury. Do they have enough pitching depth to be a factor in the NL West for the entire season?