Buehrle is a closer comp, although even he doubles Kaat's WAA through the same age. Kaat was a good pitcher, but even in the context of the Twins he doesn't stand out as a great (i.e. better than Radke). He generally didn't seem like an "ace" just part of a solid staff with Pascual, Grant, Perry, Boswell, Chance, etc. Not sure of the background, but in 1969 and 1970, he spent most of the stretch run pitching out of the bullpen, did not appear in the 1969 playoffs, and was only tenuously part of the 1970 playoff rotation (getting the final start in the sweep and being pulled after 2 innings). In addition to having a bit more "lifetime Twin" cred, he could have benefitted from a flipped outcome to the 1965 series and/or a better finish on his remarkable 1967 stretch run to give him some defining moments. Just looking at his similarity scores at B-Ref, a Kaat election to the HOF almost certainly means Tommy John has to go in as well, and Jamie Moyer would warrant strong consideration.