So what? Neither has Valdez. But the difference is, Valdez has had the opportunity.
Grissom has very little to prove as a hitter, posting a 105 OPS+ in MLB in limited action. He also posted a .921 OPS in AAA. Valdez, in a similar sample size, has posted an 83 OPS+ in MLB and a .834 OPS in AAA.
Defensively, while Grissom is an unknown, Valdez has set the bar pretty low, considering he could not catch a cold if he was naked in Norway. There is an extremely good chance that, while he may never be an all Star, Grissom is a big step up over the current situation...