That would be a nice statement except it's completely wrong. Bradley played 113 games in CF that year (he played 1 in left and a dozen in right) and hit .198. Sizemore played only 18 games in CF, 14 in LF and 24 in RF. By the time Bradley went down to Pawtucket in late August, Sizemore had been gone a couple months.
A year after first bringing him up, not a month. Swihart had some issues defensively (particularly on blocking balls in the dirt). Frankly, he didn't look any better early on this year than he did last year. Now, they may have overestimated Vazquez' ability to hit, at least so far, but I think they had decided that Vaz was the franchise future at catcher and, given the less than stellar output in LF this year, decided that Swihart was athletic enough to do the job. Unfortunately, he got hurt.