Vladimir Guerrero has played for a tenth of the season so far. Earlier I covered how well designated hitters have played when they were 36 and over years of age. Vlad has not done well so far and sits at -0.3 WAR before the game on April 20th.
It is still early and Vlad could right the ship, but the first sixteen games have not been kind. Currently he finds himself better than George Brett (1993, -0.4 WAR) and Cecil Cooper (1987, -0.6 WAR) which places him as the 24th best DH out of 26.