In the second half of 2015 Jake Arrieta went on one of the most impressive pitching runs baseball had ever seen. In fact it was the best pitched second half of all time. In his 15 starts after the All-Star break he went 12-1 with a 0.75 ERA, the lowest ERA after the break in MLB history. Arrieta's only loss came when Cole Hamels threw a no-hitter against the Cubs. Arrieta's performance was better than the second half of Bob Gibson's legendary 1968 season when he went 11-4 with a 1.19 ERA after the All-Star game.
Arrieta's dominance led to him winning the NL Cy Young award, which began an off-season conversation of whether or not he had surpassedClayton Kershaw as the best pitcher in baseball. Whenever an athlete has been great for a long time we tend to think their prime is over when a new challenger comes along attempting to exceed them. Kershaw fits this category. Over the past five seasons he won three Cy Young awards, an MVP, led the league in ERA four times, WHIP four times, strikeouts three times, and wins twice.
Despite being two years older than Kershaw, Arrieta was the new kid on the block in terms of the best pitcher in baseball conversation. Yet on April 21st of this season he threw his second no-hitter since last August and remained unbeaten until June 5th. The loss stopped a 20 game regular season winning streak that stretched 11 months. He has been the most un-hittable starter in the NL with a league leading 5.7 hits given up per nine innings. While this had led to an extremely impressive 2.10 ERA he has simply not been able to keep up with the brilliance of Kershaw.
Kershaw's season has been a joke. Here is a list of categories he leads the league in: ERA, complete games, shutouts, innings pitched, strikeouts, ERA+, FIP, WHIP, BB/9, and strikeout to walk ratio. Some of those stats are common ones that every fan can understand and some are more advanced but they are all equally impressive. But the most impressive? Kershaw's 16.11 strikeout to walk ratio would be the best ever for a single season. The current record? 11.63. In other words Kershaw is striking out more hitters while walking less at a rate we have never come close to seeing.
In terms of how he ranks directly to Arrieta it isn't as close as you would expect. The categories that Arrieta leads in, wins and hits per nine, Kershaw is right behind him. Arrieta has 12 wins to Kershaw's 11 while Kershaw is at 5.9 hits per nine, just 0.2 behind Arrieta. Meanwhile Kershaw has sizable leads in ERA (1.79 to 2.10), strikeouts (145 to 111), BB/9 (0.7 to 3.5) and strikeout to walk ratio (16.11 to 2.78). By nearly any objective standard Kershaw has been the superior pitcher in 2016. The jury is still out on whether or not he can get it done in the playoffs but barring something tragic except Kershaw to win his fourth Cy Young award in six seasons and to solidify his claim as the best pitcher in all of baseball.