Losing a reliever for a couple of weeks is never fun, but such is the nature of bullpens and those who inhabit them. Pitchers struggle and get moved down in the pecking order, suffer injuries, etc. There's a reason relievers are so dang hard to predict, unless they happen to be named Smoltz.
As it pertains to the Braves' performance on the field, this move isn't likely to have a major effect. Holmes had a peculiar line: a 6.23 ERA, but 12 strikeouts in 8 2/3 innings. Pitchers with that type of strikeout rate don't usually have ERAs over 6. How much the inflamed nerve really hurt Holmes' pitching is a matter of wild speculation at this point. The ERA would indicate something was wrong, but the strikeout numbers seem to say his stuff was still sharp.
Holmes wasn't getting the high leverage innings anyway. Bobby Cox was riding hard the arms of John Smoltz, Roberto Hernandez, Ray King, Jung Bong, and to a lesser extent, Kevin Gryboski. A quick recovery on the part of Holmes is going to be crucial for the long-term health of the Braves bullpen. Hernandez is on pace to throw 96 innings, a career high. King is on pace for 71 innings, and the still young arm of the promising lefty Bong is currently en route for 82 2/3 innings. (It could be worse. They could be Jason Grimsley, who's on pace to throw roughly 1,234 innings this year for the Royals) That's easy to understand considering the trio's early season success, and the struggles of Holmes and the other relievers in the pen. But it's not a recipe for second-half success. A Holmes' resurgence after this DL stint could take a lot of pressure off the overworked bullpen core.
The decision to call-up Joe Dawley makes some sense from an evaluative perspective. Dawley was rocked in his first major league stint earlier this year, with a 19.80 ERA that makes most Rockies' laugh derisively. But he went down to Richmond, pulled his act together, and did what he's done for the past several years: Strike hitters out (12 in 10 innings) while putting up a decent ERA. Whether or not his AAA success translates better this go-round than last will be an interesting question to see answered. The Braves lose nothing by finding out, as Dawley will only inherit the near mop-up innings heretofore occupied by Holmes and Trey Hodges.
The only really disappointing part of this move is that Buddy Hernandez didn't get a call-up. There are legitimate reasons for this. Buddy is, inexplicably, not on the 40 man roster. And calling up the younger, more exciting, prospect co-closer of Richmond so that he can sit in the bullpen and commiserate with Trey Hodges for 2 weeks isn't fair to the fans of that club. Besides, it's become painfully obvious that Buddy, like his brother-in-short Marcus Giles, is going to have to prove himself above and beyond most other prospects. And considering that the team was so awed at Buddy's first 3 seasons of pitching, which saw him strike out 222 hitters in 149 innings while allowing 2 homeruns, they left him unprotected for the Rule 5 draft, it was unreasonable to expect the organization to be impressed by a 2.20 ERA and 12.85 K/9 in Richmond.