Leading up to Spring Training for the St. Louis Cardinals, there were plenty of articles written about the incredible starting pitching depth of the Cardinals. They had seven legitimate options for the rotation, and it wasn’t a stretch to say eight. While there was always going to be competition in the rotation, Jaime Garcia’s injury opens up a much more focused competition for the Cardinals’ 5th rotation spot. The four locks for the rotation are Adam Wainwright, Lance Lynn, Shelby Miller and Michael Wacha. While another pitcher could join the discussion, the battle for the final spot is essentially between Joe Kelly and Carlos Martinez. There really is no clear favorite, as Kelly is the incumbent, but Martinez carries much greater upside. The pitcher that fails to capture the 5th slot in the rotation will likely serve as a late-inning reliever for the Cardinals, which may influence the Cardinals’ decision.

Based off Joe Kelly’s impressive performance last season it would be easy to assume he is the favorite to be the 5th starter; however, his advanced metrics do not support his traditional statistics. While Kelly pitched to a 10-5 record with a 2.69 ERA, he had an FIP of 4.01 and an unsustainable 82.4 Left on Base % (LOB%). Joe Kelly also possesses a power sinker in the mid-90s, a plus change-up and solid-average curveball. Despite this power repertoire, Kelly has never struck out many batters, as he has a career K/9 of just 6.00. This is not overly concerning, but does leave Kelly vulnerable to high variability in performance, since he is so heavily dependent upon his defense.

I have, to this point, only pointed out Kelly’s weaknesses in order tamper expectations, but in reality, Kelly is a very talented starter. Kelly is a very strong groundball pitcher (career 51.4%), which has helped him limit his Hr/9 (career .78). To this point in his career, Kelly has done a great job of limiting runs, which is all that is really important. In 2013, Kelly allowed just 3.05 runs per 9 innings. The Cardinals certainly know the concerns with Kelly, but they are also aware of his upside. While Kelly is likely to serve as a late-inning option for the Cardinals if he is not named their 5th starter, he has not been as effective as a reliever. In an admittedly small sample of just 37 innings in 2013, Kelly carried a 3.65 ERA and an opponent’s slash line of .284/.342/.435 as a reliever.

Now looking at Carlos Martinez, it is clear that Martinez is the starter with much more upside, as he can consistently reach triple digits and strike out nearly 9 batters per 9 innings. In a tiny sample of 28 1/3 innings at the Big League level last year, Martinez pitched to a 5.08 ERA, but a much better 3.08 FIP. Most of those innings came in relief, as he made just one start in the Majors, but he was still very impressive. While Martinez’s ERA was high, he was hurt by a high BABIP of .345 and a low LOB% of just 64.9%. Despite carrying substantial upside, Martinez has never thrown more than 108 IP in a professional season, which raises concerns about his ability to handle a starter’s workload for a full season. Also, unlike Kelly, Martinez is likely to thrive in a late-inning relief role, as he carried a 2.33 FIP in 23 2/3 IP as a reliever. If the two pitchers have similar evaluations at the end of spring training, then I believe Martinez will be relegated to the bullpen where he can thrive and further develop as an MLB pitcher.

While it may seem that Kelly is the front-runner to be the Cardinals’ 5th starter, it is clear that each starter has plenty of positives and negatives. Kelly’s negative traits largely revolve around regression to the mean in many areas, such as LOB% and ERA. Whereas Martinez’s positives are very similar to his negatives, as there are many questions about how well he will do as a starter full time. It is always nice to dream on a player’s potential and stuff, he must also prove he can be effective in his role and Martinez has not yet done that. This will be a fun competition to watch in spring training. I believe Kelly will come out of spring training as the Cardinals’ 5th starter because he has proven he can perform as a starter, but also because he is not as strong a fit for the bullpen. If Martinez is not named the 5th starter, he can still be a lights out reliever, whereas, Kelly may not be as effective in such a role.