The Angels have made it clear that Kotchman is their 1B going into the year and Erstad is out in CF yet again. So I don't see how Erstad will play a bulk of his AB's at 1B/DH and then go play CF against LHP. It just isn't real convenient and McPherson would have to make it happen by playing great. Something I don't see happening after his injury riddled 2005.
The point is, Rivera has been productive in the majors while McPherson hasn't. Also, Rivera hits better against RHP's, so the theory doesn't all work out. Until something changes, which I don't see happening soon, McPherson is on the bench. Well until Erstad gets hurt in the OF yet again or Rivera slumps.