The most important year in any baseball player's development comes in their 1st full season at the major league level. Teams have more games on film to look at and develop a possible game plan against him and it's up to the player to adjust to the league. This is where Robbie Ray stands at in 2016. In 2015 Ray made 23 starts at the MLB level, going 5-12 with a 3.52 ERA. A lot of the losses can be attributed to run support issues, but his ERA is backed up by a 3.53 FIP. However, more advanced metrics are skeptical of his success moving forward with a SIERA of 4.05 and an xFIP of 4.03. Ray's HR/FB rate was 7.3% in 2015, so expect some regression in that number in 2016.
What happened in 2015 is that Ray decreased his usage in the change-up and started going to his slider more. That helped to increase his strikeout rate from 14% to 21.8% in 2016. At the same time, his walk rate jumped from 8.1% to 9%. What keeps Ray from taking the next step in his development is the walk rate. His strikeout rate is 40th in MLB for starting pitchers will more than 100 innings, but his walk rate is the 18th highest in that same field. Ray is 73rd in swinging strike rate (9.0%) and 79th in first pitch strikes (60.7%), which tells me that he falls behind the count too much and when he does he lacks the ability to miss bats in hitter's counts. In order to lower the walk rate, Ray is going to need to jump ahead in the count more often so batters can't start eliminating pitches.
Ray does not lack bad stuff, his average fastball sits 94 MPH along with a slider, curveball, and change-up. Ray's slider seems to be the pitch that needs more development in 2016. It's a pitch that's been hit the hardest, as he gave up 4 of his 9 HR allowed on his slider. Patrick Corbin throws a very filthy left-handed slider, so he has someone to go to for advice on how to make that pitch better. If that slider develops into a real weapon, Ray will likely improve from a No. 4-5 starter to a No. 2-3 starter.
For Robbie Ray, the 2015 season proved that he can compete at the MLB level. With that knowledge in place 2016 is where he needs to show he belongs for the long haul. The first step is beating the competition for the final rotation spot in camp. I believe that strong competition is always good for the people involved because it makes them better players. If Ray can take that step forward in 2016, it will give the Diamondbacks a formidable rotation in both the present and the future.