"Kershaw is a dominant force in the regular season, but he’s been the complete opposite once October comes around. In 35 playoff appearances, Kershaw has an 11-12 record and a 4.31 ERA. For context, he hasn’t finished a single season with that high an ERA since his rookie year.

Kershaw allows more runs, hits, walks, and home runs in the postseason, and it’s not a small sample size.
But what’s even worse is his performance in games when the Dodgers are facing elimination. Kershaw has an atrocious 5.77 ERA in elimination games. That’s the second-highest mark in MLB history."

35th in career ERA and 36th in strikeouts in MLB history, not sure how that makes him the best of all time.