Here's a look at what each of the four teams still in the NL West playoff hunt stand to gain from the roster expansion:
The Dodgers have one of the best farm systems in the game today. However, due to a flurry of injuries throughout the season, much of the Dodgers' ML-ready talent has already been contributing for some time. Andre Ethier has hit .332 in 100 games for LA, and is among the leading contenders in a particularly strong National League Rookie of the Year race. After struggling with his control in his first month in the big leagues, Chad Billingsley has become the pitcher everyone had predicted he would over his last few starts. Takashi Saito stepped in for the injured Eric Gagne and the inconsistent Danys Baez and become one of the league's best closers.
Among those who had been called up previously, Matt Kemp had shown useful power in a utility role, but James Loney and Willy Aybar found hitting in Los Angeles a bit more difficult than in Las Vegas. So while 2B Sergio Garcia and 3B Andy LaRoche are currently lighting up Las Vegas, whether they can do the same in one of the more extreme pitcher's parks in the majors is certainly questionable.
As for possible pitcher callups, Hong-Chih Kuo continues to impress in the minors, but he doesn't do much in his ML stints. Eric Hull, a reliever off most people's radar screen, has performed well and could be called up. But the Dodgers may not want to waste a 40-man roster slot on someone who is unlikely to draw much interest in the Rule V draft this winter.
Overall, having guys like Kemp, Loney, and Aybar back on the roster will give manager Grady Little a bit more flexibility regarding pinch hitting and such, but don't expect a major impact from the Dodgers' September callups as a whole.
Here's the team that stands to gain the most from expanded rosters. Jack Cust, Jon Knott, Paul McAnulty, and Terrmel Sledge have all been forces for the Portland Beavers this season. There is some concern that Cust and Sledge are Triple-A players and they will experience pitcher's park shock similar to how Dodgers prospects have, but out of these four guys, one or two could become difference makers. Jon Knott is particularly important, as San Diego lacks a solid right handed bat off of the bench.
Pitching-wise, there's not a whole lot to get excited about now that Cla Meredith is already dominating the big leagues. But with recent injuries to Chan Ho Park and Scott Williamson, even so-so pitchers like Tim Stauffer and Dewan Brazelton may be able to step in and eat up some garbage innings out of the bullpen, saving their good relievers for the close games.
No team in the NL West should be looking forward to September as much as the San Diego Padres.
When September rolls around, Lance Niekro and Jason Ellison should once again get an opportunity to prove themselves at the big league level. The trouble is, as well as they've both hit AAA pitching, neither one has worked on their plate patience. Their inability to walk and see a lot of pitches was the reason that these guys weren't successful in their first stints, and we shouldn't expect that to change this go-'round.
On the other hand, the ability to bring up a defensive catcher like Yamid Haad could be key, as neither Todd Greene or Eliezer Alfonzo looks great behind the dish. Either Michael Tejera or Matt Palmer would serve as an improvement over Jamey Wright in the fifth starter's role. However if the Giants were going to make that kind of switch they would have done so by now. At least they could be used in long relief when Wright or Cain gets knocked out early in a ballgame.
Considering how little the Giants have in the upper levels of their organization, they will receive a decent sized boost from the expanded September rosters.
Like the Dodgers, most of Arizona's premium upper level talent has already seen big league action this year. Enrique Gonzalez, Stephen Drew, Carlos Quentin, Tony Pena, and Chris Young are the main players who began the year in the minors that are now key contributors to the big league ballclub.
Dustin Nippert and Alberto Callaspo have each seen time at the show, and will each be able to contribute full time come September. However, Nippert will likely work out of the bullpen now that the Diamondbacks have Livan Hernandez and Callaspo won't see to much action with Craig Counsell back as the main utility infielder. Scott Hairston should receive another chance as well. Randy Choate is certain to get another look as a lefty out of the D'Backs' right hand-dominated pen; He's been terrific lately for the Sidewinders.
Two guys who haven't surfaced yet, Miguel Montero and Chris Carter, could be the key additions of September. Montero actually began the year at AA, but has really impressed this year. It's always nice to have a third catcher on the roster, especially one that is talented in all facets of the game. Carter has had as good of an offensive season as many of the Sidewinders players that have been called up already. The only reason Carter hasn't yet seen any major league action is because he is blocked by Conor Jackson at first base. With expanded rosters, he can be used only as a pinch hitter, although Tony Clark is off the DL and should see most of the at bats in that role.
Again, we see how the 40-man roster will benefit the Diamondbacks, but it doesn't seem likely that it will improve the team as much as San Diego's likely additions.
Read more from Keith Glab at BaseballEvolution.com