Dodgers lefty ace Clayton Kershaw on Friday passed up the chance to become a free agent and instead signed a contract extension with L.A. that will guarantee him more than $90 million. So with Kershaw off the market, another NL West left-hander becomes the undisputed best starting pitcher on the free agent market his offseason: Patrick Corbin of the Diamondbacks

Corbin, who turned 29 in July, hits the market with a career ERA+ of 109 and a K/BB ratio of 3.31 across parts of six big-league seasons, all with Arizona. What adds to his value, though, is that he's coming off a career year in 2018 ... 

Patrick Corbin
WAS • SP • #46
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Corbin topped 200 innings for the second time his career, and that 3.15 ERA scales to an ERA+ of 137, which was good for seventh place on the NL leaderboard. Also note that impressive K/BB ratio of 5.13, which ranked third in the NL. It's that dominance at the command-and-control level that bodes well for Corbin moving forward. 

Speaking of which, let's turn to FIP for a moment. In general terms, FIP, which stands for fielding-independent pitching, is what a pitcher's ERA should be if you emphasize what's most under the pitcher's control (i.e., strikeouts and walks) and correct for things like luck, defense and sequencing. It's a good indicator of a pitcher's underlying basic skills on the mound, and it usually predicts future ERAs better than ERA itself does. As for Corbin, in 2018 he had an FIP of 2.47, which in the NL trailed only Jacob deGrom's mark of 1.98. 

Corbin's a bit unusual among starters, in that he throws his hard slider a plurality of the time. He also throws a sinker, four-seamer, curve, and occasional changeup. He also puts up strong ground-ball numbers. 

Beyond that, Corbin's success in 2018 wasn't exactly out of nowhere. He's a former second-rounder who as a 23-year-old in 2013 worked 208 1/3 innings and made the All-Star team. Corbin does have a Tommy John surgery in his history -- early 2014 -- and as is often the case his command was slow to return. This past season, though, he proved he was back to normal and then some. Since coming off the DL in July of 2015 following his recovery, he's been fully healthy. 

Really, you could argue that since Corbin is more than a full year younger than Kershaw with much less mileage on his arm (and somewhat better velocity at this juncture), he was going to fetch a bigger contract than the three-time Cy Young winner. With Kershaw now spoken for, though, Corbin is without question the most coveted starting pitcher available. 

Speaking of which, the Yankees have been heavily rumored in the early going when it comes to fits for Corbin, but a frontline lefty is of interest to almost any team with designs on contention. Thanks in part to Corbin's leveling up this past season, he's likely in line for a nine-figure contract this offseason.