I was in the midst of posting this response in the comments section, and I figured it was better suited as a post...
I know a lot of people have been raising questions about Giles recently, as he's had a miserable start to his season.
I know he's 38, but this is also a very small sample that may not be indicative of anything.
In 2005 Giles hit .145/.294/205 over 100 or so pa's from early April to early May.
In 2006 Giles hit .115/.303/.135 in roughly 70 pa's from late June through early July.
In 2007 Giles hit .175/.273/.330 in more than 100 pa's from early Sept until the end of the season.
In 2008 Giles hit .218/.365/.308 in more than 70 pa's in late April through mid-May.
The point is that just about anything can happen to just about anyone over a span of 150 plate appearances, and in fact, something similar has happened to Giles in each of the past four seasons.
Here's another example: in 2003 when I was still in Oakland, we had the reigning AL MVP, Miguel Tejada, playing shortstop. After his first 120 pa's or so of the season, he was hitting .157/.229/.287 - the reigning MVP! By the end of the season he was up to .278/.336/.472 - right in line with his career norms.
Though Brian hasn't swung the bat the way all of us are accustomed to seeing, he has had some bad luck and his approach has improved. In the first 15 games Brian walked just four times and struck out 10. That is unusual for a guy who walked more than he has struck out over the course of his entire ML career. However, in the past 16 games Brian has walked nine times and struck out five. That's more like it and could be a sign that he's seeing the ball better. Then again, that could just be small sample sizes playing tricks on us...
The real point is that we're generally better served by looking at the body of work over a longer time frame than we are by focusing on the last 100 pa's. Furthermore, bad streaks get exacerbated early in the season because the numbers on the scoreboard look so terrible. If a player has a tough stretch in July that takes his average from .280 down to .255, it doesn't get nearly as much attention.
All of that doesn't mean that we're blind to changes of skill level, especially as players age. However, it does mean that players with long track records of success ought to be given more leeway before making irrevocable decisions.